A tire with noise-reducing main grooves (100, 200, 300, 400), the tire comprising: a groove portion (110. 120, 130, 140) which is formed to extend circumferentially along a circumference of a tire tread; and a plurality of knurled portions (120, 220, 320, 420) which are formed on bottom and side surfaces of the groove portion (110. 120, 130, 140), wherein the plurality of knurled portions (120, 220, 320, 420) are configured to reduce noise energy by narrowing an air path formed when the groove portion (110. 120, 130, 140) and the ground contact each other, wherein each of the knurled portions (120, 220, 320, 420) comprises: a first protrusion (121, 221, 321, 421) which is formed on the bottom surface of the groove portion (110. 120, 130, 140) and extends in a width direction of the groove portion (110. 120, 130, 140) and extends in a diagonal direction; a second protrusion (122, 222, 322, 422) which is formed to extend in a height direction of one side of the groove portion (110. 120, 130, 140) and extends from one side of the first protrusion (121, 221, 321, 421) in the same direction as that of the first protrusion (121, 221, 321, 421); and a third protrusion (123, 223, 323, 423) which is formed to extend in a height direction of the other side of the groove portion (110. 120, 130, 140) and extends from the other side of the first protrusion (121, 221, 321, 421) in the same direction as that of the first protrusion (121, 221, 321, 421), wherein the plurality of the knurled portions (120, 220, 320, 420) are formed to extend in zigzags in a longitudinal direction of the groove portion (110. 120, 130, 140), and are directly connected to each other, characterized in that protrusion heights of the second protrusion (122, 222, 322, 422) and the third protrusion (123, 223, 323, 423) decrease gradually toward upper portions thereof. a groove portion (110. 120, 130, 140) which is formed to extend circumferentially along a circumference of a tire tread; and a plurality of knurled portions (120, 220, 320, 420) which are formed on bottom and side surfaces of the groove portion (110. 120, 130, 140), wherein the plurality of knurled portions (120, 220, 320, 420) are configured to reduce noise energy by narrowing an air path formed when the groove portion (110. 120, 130, 140) and the ground contact each other, wherein each of the knurled portions (120, 220, 320, 420) comprises: a first protrusion (121, 221, 321, 421) which is formed on the bottom surface of the groove portion (110. 120, 130, 140) and extends in a width direction of the groove portion (110. 120, 130, 140) and extends in a diagonal direction; a second protrusion (122, 222, 322, 422) which is formed to extend in a height direction of one side of the groove portion (110. 120, 130, 140) and extends from one side of the first protrusion (121, 221, 321, 421) in the same direction as that of the first protrusion (121, 221, 321, 421); and a third protrusion (123, 223, 323, 423) which is formed to extend in a height direction of the other side of the groove portion (110. 120, 130, 140) and extends from the other side of the first protrusion (121, 221, 321, 421) in the same direction as that of the first protrusion (121, 221, 321, 421), a first protrusion (121, 221, 321, 421) which is formed on the bottom surface of the groove portion (110. 120, 130, 140) and extends in a width direction of the groove portion (110. 120, 130, 140) and extends in a diagonal direction; a second protrusion (122, 222, 322, 422) which is formed to extend in a height direction of one side of the groove portion (110. 120, 130, 140) and extends from one side of the first protrusion (121, 221, 321, 421) in the same direction as that of the first protrusion (121, 221, 321, 421); and a third protrusion (123, 223, 323, 423) which is formed to extend in a height direction of the other side of the groove portion (110. 120, 130, 140) and extends from the other side of the first protrusion (121, 221, 321, 421) in the same direction as that of the first protrusion (121, 221, 321, 421), wherein the plurality of the knurled portions (120, 220, 320, 420) are formed to extend in zigzags in a longitudinal direction of the groove portion (110. 120, 130, 140), and are directly connected to each other, characterized in that protrusion heights of the second protrusion (122, 222, 322, 422) and the third protrusion (123, 223, 323, 423) decrease gradually toward upper portions thereof.