The invention relates to a multifunction sander, which comprises a shell, a motor arranged in the shell, a switch for controlling the bidirectional rotation of the motor, a first drive shaft rotated by the drive of the motor, an eccentric device in matching connection with the first drive shaft, a polishing base plate in matching with the eccentric device and a swinging rack elastically connectedwith the shell. A unidirectional clutch is arranged between the eccentric device and the swinging rack; when the motor rotates along the first direction, the unidirectional clutch makes the swinging rack and the polishing base plate matched and connected so as to realize platy sanding; and when the motor rotates along the second direction, the unidirectional clutch makes the swinging rack separated from the polishing base plate so as to realize round sanding. Therefore, the multifunction sander can conveniently perform the switch of different functions of platy sanding and round sanding, has a simple structure, and reduces the cost.