diff --git a/cnpj.go b/cnpj.go
new file mode 100644
index 0000000..99b627c
--- /dev/null
+++ b/cnpj.go
@@ -0,0 +1,125 @@
+package brazil
+
+import (
+	"math/rand"
+	"regexp"
+	"strconv"
+	"time"
+)
+
+// CNPJ struct
+type cnpj struct {
+	number cnpjNumber
+	valid  bool
+}
+
+func (c cnpj) Number(mask bool) string {
+	if c.valid && mask {
+		return string(c.number[:2]) +
+			"." +
+			string(c.number[2:5]) +
+			"." +
+			string(c.number[5:8]) +
+			"/" +
+			string(c.number[8:12]) +
+			"-" +
+			string(c.number[12:])
+	}
+	return string(c.number)
+}
+
+func ParseCNPJ(number string) (cnpj, error) {
+	number = regexp.MustCompile(`[^0-9]`).ReplaceAllString(number, "")
+
+	if len(number) != 14 {
+		return cnpj{}, errIncorrectLenghtCNPJNumber
+	}
+
+	cnpjNumber := cnpjNumber(number)
+
+	if !cnpjNumber.hasValidFirstDigit() {
+		return cnpj{}, errInvalidCNPJFirstDigit
+	}
+
+	if !cnpjNumber.hasValidSecondDigit() {
+		return cnpj{}, errInvalidCNPJSecondDigit
+	}
+
+	return cnpj{
+		number: cnpjNumber,
+		valid:  true,
+	}, nil
+}
+
+func RandomCNPJNumber(mask bool) string {
+	var multipliers = []int{6, 5, 4, 3, 2, 9, 8, 7, 6, 5, 4, 3, 2}
+
+	source := rand.NewSource(time.Now().UnixNano())
+	r := rand.New(source)
+	cnpjNumber := int(r.Int63n(899999999999) + 100000000000)
+	cnpjString := strconv.Itoa(cnpjNumber)
+
+	// Calculate first digit
+	sum := 0
+	for i := 0; i < 12; i++ {
+		number, _ := strconv.Atoi(string(cnpjString[i]))
+		sum += number * multipliers[i+1]
+	}
+	firstDigit := 0
+	if sum%11 >= 2 {
+		firstDigit = 11 - sum%11
+	}
+
+	// Calculate second digit
+	sum = 0
+	for i := 0; i < 12; i++ {
+		number, _ := strconv.Atoi(string(cnpjString[i]))
+		sum += number * multipliers[i]
+	}
+	sum += firstDigit * multipliers[12]
+	secondDigit := 0
+	if sum%11 >= 2 {
+		secondDigit = 11 - sum%11
+	}
+
+	if mask {
+		return cnpjString[:2] + "." + cnpjString[2:5] + "." + cnpjString[5:8] + "/" + cnpjString[8:12] + "-" + strconv.Itoa(firstDigit) + strconv.Itoa(secondDigit)
+	}
+	return cnpjString + strconv.Itoa(firstDigit) + strconv.Itoa(secondDigit)
+}
+
+type cnpjNumber string
+
+func (c cnpjNumber) hasValidFirstDigit() bool {
+	var (
+		multipliers = []int{5, 4, 3, 2, 9, 8, 7, 6, 5, 4, 3, 2}
+		sum         int
+	)
+
+	for i := 0; i < 12; i++ {
+		cnpjDigit, _ := strconv.Atoi(string(c[i]))
+		sum += cnpjDigit * multipliers[i]
+	}
+	if sum%11 < 2 {
+		return string(c[12]) == strconv.Itoa(0)
+	}
+
+	return string(c[12]) == strconv.Itoa(11-sum%11)
+}
+
+func (c cnpjNumber) hasValidSecondDigit() bool {
+	var (
+		multipliers = []int{6, 5, 4, 3, 2, 9, 8, 7, 6, 5, 4, 3, 2}
+		sum         int
+	)
+
+	for i := 0; i < 13; i++ {
+		cnpjDigit, _ := strconv.Atoi(string(c[i]))
+		sum += cnpjDigit * multipliers[i]
+	}
+
+	if sum%11 < 2 {
+		return string(c[13]) == strconv.Itoa(0)
+	}
+	return string(c[13]) == strconv.Itoa(11-sum%11)
+}
diff --git a/cnpj_test.go b/cnpj_test.go
new file mode 100644
index 0000000..3b6f823
--- /dev/null
+++ b/cnpj_test.go
@@ -0,0 +1,108 @@
+package brazil_test
+
+import (
+	"testing"
+
+	. "flavioltonon/go-brazil"
+
+	. "github.com/smartystreets/goconvey/convey"
+)
+
+func TestParseCNPJ(t *testing.T) {
+	Convey("Given a string named s", t, func() {
+		var s string
+
+		Convey("If s is empty", func() {
+			s = ""
+
+			Convey("And the function ParseCNPJ is called using it as an argument", func() {
+				cnpj, err := ParseCNPJ(s)
+
+				Convey("It should return an error", func() {
+					So(err, ShouldNotEqual, nil)
+
+					Convey("And the CNPJ struct number should be empty", func() {
+						So(cnpj.Number(false), ShouldEqual, "")
+					})
+				})
+			})
+		})
+
+		Convey("If s is a CNPJ number with an invalid first digit", func() {
+			s = "11222333000171"
+
+			Convey("And the function ParseCNPJ is called using it as an argument", func() {
+				cnpj, err := ParseCNPJ(s)
+
+				Convey("It should return an error", func() {
+					So(err, ShouldNotEqual, nil)
+
+					Convey("And the CNPJ struct number should be empty", func() {
+						So(cnpj.Number(false), ShouldEqual, "")
+					})
+				})
+			})
+		})
+
+		Convey("If s is a CNPJ number with an invalid second digit", func() {
+			s = "11222333000182"
+
+			Convey("And the function ParseCNPJ is called using it as an argument", func() {
+				cnpj, err := ParseCNPJ(s)
+
+				Convey("It should return an error", func() {
+					So(err, ShouldNotEqual, nil)
+
+					Convey("And the CNPJ struct number should be empty", func() {
+						So(cnpj.Number(false), ShouldEqual, "")
+					})
+				})
+			})
+		})
+
+		Convey("If s is a valid CNPJ number", func() {
+			s = "11222333000181"
+
+			Convey("And the function ParseCNPJ is called using it as an argument", func() {
+				cnpj, err := ParseCNPJ(s)
+
+				Convey("It should not return an error", func() {
+					So(err, ShouldEqual, nil)
+
+					Convey("And the CNPJ struct number should exist", func() {
+						So(cnpj.Number(false), ShouldEqual, "11222333000181")
+						So(cnpj.Number(true), ShouldEqual, "11.222.333/0001-81")
+					})
+				})
+			})
+		})
+	})
+}
+
+func TestRandomCNPJNumber(t *testing.T) {
+	Convey("Given the function RandomCNPJNumber", t, func() {
+		Convey("If its mask argument equals true", func() {
+			number := RandomCNPJNumber(true)
+
+			Convey("It should return a valid CNPJ number", func() {
+				cnpj, err := ParseCNPJ(number)
+
+				So(err, ShouldEqual, nil)
+				So(cnpj.Number(false), ShouldNotEqual, "")
+				So(cnpj.Number(true), ShouldNotEqual, "")
+			})
+		})
+
+		Convey("If its mask argument equals false", func() {
+			number := RandomCNPJNumber(false)
+
+			Convey("It should return a valid CNPJ number", func() {
+				cnpj, err := ParseCNPJ(number)
+
+				So(err, ShouldEqual, nil)
+				So(cnpj.Number(false), ShouldNotEqual, "")
+				So(cnpj.Number(true), ShouldNotEqual, "")
+			})
+		})
+	})
+}