A driver unit (2) for driving staples and a clincher unit (3) for clinching the legs of staples are vertically separated from each other. The driver unit (2) and a clincher unit (3) are provided with drive motors (M1, M2), respectively. Drive shafts (12, 30) for driving the driver unit (2) and clincher unit (3) are formed with encoders (21, 40) that produce pulse signals (P1, P2) by rotation of the drive shafts, respectively. The pulse signals (P1, P2) are inputted into control device (47), where they are counted. On the basis of the count value, the control device (47) controls the drive motors (M1, M2).