An exemplary clamp includes a holder, a moving unit, a fixing arm, and a driving unit. The moving unit includes a push block, a connecting member, and a guiding member. The guiding member is fixed on the holder. The connecting member connects the push block and the guiding member. The push block includes a slanted side surface. The push block is guided to move by the guiding member. The slanted side surface of the push block interacts with the connecting member. The fixing arm is fixed to the connecting member. The driving unit is connected to the push block. The driving unit is capable of moving the push block of the moving unit.