A cleaning unit comprising: a power module; a body part that is connected to the power module to rotate and includes a first through- hole (215, 315, 415) defined in an outer circumferential surface thereof; a shaft (220, 320, 420) that is inserted into a hollow hole of the body part in a lengthwise direction of the body part; a brush assembly in contact with the outer circumferential surface of the body part along the lengthwise direction of the body part; characterized in that the cleaning unit further comprises: a first cam (235, 335, 435) extending from a surface in contact with the outer circumferential surface of the body part toward an outer circumferential surface of the shaft (220, 320, 420) through the first through-hole (215, 315, 415); and a second cam (223, 323, 423) extending from the outer circumferential surface of the shaft (220, 320, 420) toward the first cam (235, 335, 435), wherein the shaft (220, 320. 420) performs a reciprocating motion in the body part in the lengthwise direction of the body part, wherein one of the first cam (235, 335, 435) and the second cam (223, 323, 423) is provided at one side thereof with an inclined surface that is inclined along the lengthwise direction of the body part, and wherein a remaining one of the first cam (235, 335, 435) and the second cam (223, 323, 423) presses the inclined surface as the shaft (220, 320, 420) performs the reciprocating motion, so that the brush assembly moves upward and downward in a radial direction of the shaft (220, 320, 420). a power module; a body part that is connected to the power module to rotate and includes a first through- hole (215, 315, 415) defined in an outer circumferential surface thereof; a shaft (220, 320, 420) that is inserted into a hollow hole of the body part in a lengthwise direction of the body part; a brush assembly in contact with the outer circumferential surface of the body part along the lengthwise direction of the body part; characterized in that the cleaning unit further comprises: a first cam (235, 335, 435) extending from a surface in contact with the outer circumferential surface of the body part toward an outer circumferential surface of the shaft (220, 320, 420) through the first through-hole (215, 315, 415); and a second cam (223, 323, 423) extending from the outer circumferential surface of the shaft (220, 320, 420) toward the first cam (235, 335, 435), wherein the shaft (220, 320. 420) performs a reciprocating motion in the body part in the lengthwise direction of the body part, wherein one of the first cam (235, 335, 435) and the second cam (223, 323, 423) is provided at one side thereof with an inclined surface that is inclined along the lengthwise direction of the body part, and wherein a remaining one of the first cam (235, 335, 435) and the second cam (223, 323, 423) presses the inclined surface as the shaft (220, 320, 420) performs the reciprocating motion, so that the brush assembly moves upward and downward in a radial direction of the shaft (220, 320, 420). a first cam (235, 335, 435) extending from a surface in contact with the outer circumferential surface of the body part toward an outer circumferential surface of the shaft (220, 320, 420) through the first through-hole (215, 315, 415); and a second cam (223, 323, 423) extending from the outer circumferential surface of the shaft (220, 320, 420) toward the first cam (235, 335, 435), wherein the shaft (220, 320. 420) performs a reciprocating motion in the body part in the lengthwise direction of the body part, wherein one of the first cam (235, 335, 435) and the second cam (223, 323, 423) is provided at one side thereof with an inclined surface that is inclined along the lengthwise direction of the body part, and wherein a remaining one of the first cam (235, 335, 435) and the second cam (223, 323, 423) presses the inclined surface as the shaft (220, 320, 420) performs the reciprocating motion, so that the brush assembly moves upward and downward in a radial direction of the shaft (220, 320, 420).