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