Disclosed is a cleaning unit comprising a variable brush portion. The cleaning unit according to an embodiment of the present invention comprises a shaft capable of reciprocating along an axial direction, wherein a first cam protrudes from the outer circumferential surface of the shaft. In addition, the brush portion is arranged on the outer circumferential surface of a body member surrounding the shaft, and the brush portion includes a second cam engaged with the first cam. When the shaft is moved in the axial direction, the first cam pushes the second cam in a radial direction, whereby the brush portion may protrude in the radial direction. That is, as the shaft reciprocates in the axial direction, the length of the brush portion protruding from the outer circumferential surface of the body member may vary.