An electric stapler is operated by the steps of: a paper bundle pinching step of relatively moving a table part (10) and a driver unit (3) and also pinching a paper bundle (19); a staple separation step of folding a staple into U-shape by a forming plate (8) and also separating the folded U-shape staple (22) from a staple sheet (20) by moving a driver (7); a penetration step of penetrating legs (24) of the staple (22) into the paper bundle (19) by further moving the driver (7); a clinch step of inward folding the legs (24) penetrating through the paper bundle (19) by a clinch device (5); and a paper bundle releasing step of releasing the paper bundle (19). A relative movement of the table part (10) and the driver unit (3), the forming plate (8), the driver (7), and the clinch device are powered by a single motor (13). A driving speed of the motor (13) in the steps excluding the penetration step and the clinch step is slower than the driving speed of the motor (13) in the penetration step and the clinch step.