diff --git a/known_sig/orthoses/trace/attribute.rbs b/known_sig/orthoses/trace/attribute.rbs
index e96b069..781f4bc 100644
--- a/known_sig/orthoses/trace/attribute.rbs
+++ b/known_sig/orthoses/trace/attribute.rbs
@@ -2,6 +2,9 @@ module Orthoses
   class Trace
     class Attribute
       include Orthoses::Trace::Targetable
+
+      def initialize: (Orthoses::_Call loader, patterns: Array[String], ?sort_union_types: bool?) -> void
+      def call: () -> Orthoses::store
     end
   end
 end
diff --git a/known_sig/orthoses/trace/method.rbs b/known_sig/orthoses/trace/method.rbs
index 9016e6e..f8a168f 100644
--- a/known_sig/orthoses/trace/method.rbs
+++ b/known_sig/orthoses/trace/method.rbs
@@ -2,6 +2,9 @@ module Orthoses
   class Trace
     class Method
       include Orthoses::Trace::Targetable
+
+      def initialize: (Orthoses::_Call loader, patterns: Array[String], ?sort_union_types: bool?) -> void
+      def call: () -> Orthoses::store
     end
   end
 end
diff --git a/lib/orthoses/trace/attribute.rb b/lib/orthoses/trace/attribute.rb
index 4f1280f..56ab1b0 100644
--- a/lib/orthoses/trace/attribute.rb
+++ b/lib/orthoses/trace/attribute.rb
@@ -23,9 +23,10 @@ def attr_writer(*names)
 
       include Targetable
 
-      def initialize(loader, patterns:)
+      def initialize(loader, patterns:, sort_union_types: true)
         @loader = loader
         @patterns = patterns
+        @sort_union_types = sort_union_types
 
         @captured_dict = Hash.new { |h, k| h[k] = Hash.new { |hh, kk| hh[kk] = [] } }
       end
@@ -45,6 +46,7 @@ def call
 
         @captured_dict.each do |mod_name, captures|
           captures.each do |(kind, prefix, name), types|
+            types.sort! if @sort_union_types
             injected = Utils::TypeList.new(types).inject
             store[mod_name] << "#{kind} #{prefix}#{name}: #{injected}"
           end
diff --git a/lib/orthoses/trace/attribute_test.rb b/lib/orthoses/trace/attribute_test.rb
index 50af341..c36ef07 100644
--- a/lib/orthoses/trace/attribute_test.rb
+++ b/lib/orthoses/trace/attribute_test.rb
@@ -12,6 +12,10 @@ class Bar
         attr_accessor :attr_acce_publ
       end
 
+      class Baz
+        attr_accessor :multi_types
+      end
+
       attr_accessor :attr_acce_publ
       attr_reader :attr_read_publ
       attr_writer :attr_writ_publ
@@ -20,6 +24,7 @@ class << self
       end
 
       attr_accessor :attr_acce_priv
+
       private :attr_acce_priv
 
       def initialize
@@ -52,7 +57,7 @@ def test_attribute(t)
     expect = <<~RBS
       class TraceAttributeTest::Foo
         attr_accessor attr_acce_priv: Integer
-        attr_accessor attr_acce_publ: Symbol | String
+        attr_accessor attr_acce_publ: String | Symbol
         attr_reader attr_read_publ: Symbol
         attr_writer attr_writ_publ: Integer
         attr_accessor self.self_attr_acce_publ: Integer?
@@ -66,4 +71,52 @@ class TraceAttributeTest::Foo::Bar
       t.error("expect=\n```rbs\n#{expect}```\n, but got \n```rbs\n#{actual}```\n")
     end
   end
+
+  def test_union_sort(t)
+    store1 = Orthoses::Trace::Attribute.new(->{
+      LOADER_ATTRIBUTE.call
+      baz = Foo::Baz.new
+      baz.multi_types = 0
+      baz.multi_types = '1'
+
+      Orthoses::Utils.new_store
+    }, patterns: ['TraceAttributeTest::Foo::Baz']).call
+
+    store2 = Orthoses::Trace::Attribute.new(->{
+      LOADER_ATTRIBUTE.call
+      baz = Foo::Baz.new
+      baz.multi_types = '1'
+      baz.multi_types = 0
+
+      Orthoses::Utils.new_store
+    }, patterns: ['TraceAttributeTest::Foo::Baz']).call
+
+    expect = store1.map { _2.to_rbs }.join("\n")
+    actual = store2.map { _2.to_rbs }.join("\n")
+    unless expect == actual
+      t.error("expect=\n```rbs\n#{expect}```\n, but got \n```rbs\n#{actual}```\n")
+    end
+  end
+
+  def test_without_union_sort(t)
+    store = Orthoses::Trace::Attribute.new(->{
+      LOADER_ATTRIBUTE.call
+      baz = Foo::Baz.new
+                            # The order of the union types will be the following
+      baz.multi_types = '1' # String
+      baz.multi_types = 0   # Integer
+
+      Orthoses::Utils.new_store
+    }, patterns: ['TraceAttributeTest::Foo::Baz'], sort_union_types: false).call
+
+    expect = store.map { _2.to_rbs }.join("\n")
+    actual = <<~RBS
+      class TraceAttributeTest::Foo::Baz
+        attr_accessor multi_types: String | Integer
+      end
+    RBS
+    unless expect == actual
+      t.error("expect=\n```rbs\n#{expect}```\n, but got \n```rbs\n#{actual}```\n")
+    end
+  end
 end
diff --git a/lib/orthoses/trace/method.rb b/lib/orthoses/trace/method.rb
index 68b39c4..7a1e8de 100644
--- a/lib/orthoses/trace/method.rb
+++ b/lib/orthoses/trace/method.rb
@@ -7,9 +7,10 @@ class Method
       Info = Struct.new(:key, :op_name_types, :raised, keyword_init: true)
       include Targetable
 
-      def initialize(loader, patterns:)
+      def initialize(loader, patterns:, sort_union_types: true)
         @loader = loader
         @patterns = patterns
+        @sort_union_types = sort_union_types
 
         @stack = []
         @args_return_map = Hash.new { |h, k| h[k] = [] }
@@ -79,6 +80,7 @@ def build_method_definitions
 
         @args_return_map.map do |(mod_name, kind, visibility, method_id), type_samples|
           type_samples.uniq!
+          type_samples.sort! if @sort_union_types
           method_types = type_samples.map do |(op_name_types, return_type)|
             required_positionals = []
             optional_positionals = []
diff --git a/lib/orthoses/trace/method_test.rb b/lib/orthoses/trace/method_test.rb
index e8e7466..2be18c4 100644
--- a/lib/orthoses/trace/method_test.rb
+++ b/lib/orthoses/trace/method_test.rb
@@ -44,6 +44,15 @@ def if_raise(a)
         end
       end
 
+      def multi_types(key)
+        {
+          0 => 0,
+          1 => '1',
+          '2' => '2',
+          '3' => 3,
+        }[key]
+      end
+
       private
 
       def priv(bool)
@@ -131,4 +140,60 @@ def test_raise_first(t)
       Orthoses::Utils.new_store
     }, patterns: ['TraceMethodTest']).call
   end
+
+  def test_union_sort(t)
+    store1 = Orthoses::Trace::Method.new(-> {
+      LOADER_METHOD.call
+      m = M.new(100)
+      m.multi_types 0
+      m.multi_types 1
+      m.multi_types '2'
+      m.multi_types '3'
+
+      Orthoses::Utils.new_store
+    }, patterns: ['TraceMethodTest::M']).call
+
+    store2 = Orthoses::Trace::Method.new(-> {
+      LOADER_METHOD.call
+      m = M.new(100)
+      m.multi_types '3'
+      m.multi_types '2'
+      m.multi_types 1
+      m.multi_types 0
+
+      Orthoses::Utils.new_store
+    }, patterns: ['TraceMethodTest::M']).call
+
+    expect = store1.map { _2.to_rbs }.join("\n")
+    actual = store2.map { _2.to_rbs }.join("\n")
+    unless expect == actual
+      t.error("expect=\n```rbs\n#{expect}```\n, but got \n```rbs\n#{actual}```\n")
+    end
+  end
+
+  def test_without_union_sort(t)
+    store = Orthoses::Trace::Method.new(-> {
+      LOADER_METHOD.call
+      m = M.new(100)
+                        # The order of the union types will be the following
+      m.multi_types '3' # (String) -> Integer
+      m.multi_types '2' # (String) -> String
+      m.multi_types 1   # (Integer) -> String
+      m.multi_types 0   # (Integer) -> Integer
+
+      Orthoses::Utils.new_store
+    }, patterns: ['TraceMethodTest::M'], sort_union_types: false).call
+
+    actual = store.map { _2.to_rbs }.join("\n")
+    expect = <<~RBS
+      class TraceMethodTest::M
+        private def initialize: (Integer a) -> void
+        def multi_types: (String key) -> (Integer | String)
+                       | (Integer key) -> (String | Integer)
+      end
+    RBS
+    unless expect == actual
+      t.error("expect=\n```rbs\n#{expect}```\n, but got \n```rbs\n#{actual}```\n")
+    end
+  end
 end
diff --git a/sig/orthoses/trace.rbs b/sig/orthoses/trace.rbs
index ede5608..dad4105 100644
--- a/sig/orthoses/trace.rbs
+++ b/sig/orthoses/trace.rbs
@@ -10,9 +10,10 @@ end
 class Orthoses::Trace::Attribute
   @loader: untyped
   @patterns: untyped
+  @sort_union_types: untyped
   @captured_dict: untyped
-  def initialize: (untyped loader, patterns: untyped) -> void
-  def call: () -> untyped
+  def initialize: (Orthoses::_Call loader, patterns: Array[String], ?sort_union_types: bool?) -> void
+  def call: () -> Orthoses::store
   private def build_trace_hook: () -> untyped
   include Orthoses::Trace::Targetable
 end
@@ -30,11 +31,12 @@ end
 class Orthoses::Trace::Method
   @loader: untyped
   @patterns: untyped
+  @sort_union_types: untyped
   @stack: untyped
   @args_return_map: untyped
   @alias_map: untyped
-  def initialize: (untyped loader, patterns: untyped) -> void
-  def call: () -> untyped
+  def initialize: (Orthoses::_Call loader, patterns: Array[String], ?sort_union_types: bool?) -> void
+  def call: () -> Orthoses::store
   private def build_trace_point: () -> untyped
   private def build_members: () -> untyped
   private def build_method_definitions: () -> untyped