Two slide bases (106) synchronizingly traveled on linear guides (105) arranged upwardly and downwardly in parallel with each other are rotatably attached with a clincher unit (107) and a driver unit (104) and provided with a click stop mechanism for fixing the clincher unit (103) and the driver unit (104) at a 0 degree position or a 45 degree rotated position. Respective outer peripheral portion thereof are provided with claw portions (119), (120), in correspondence with the 0 degree position and the 45 degree rotated position and a stopper pin (121) is arranged at a traveling path. When the driver unit and the clincher unit are traveled from an initial position to a skewed binding position, the 0 degree claw portion 119 impinges on the stopper pin (121) and the driver unit and the clincher unit are rotated to the 45 degree rotated position to fix. When the driver unit and the clincher unit are traveled reversely to the initial position, the 45 degree claw portion (120) impinges on the stopper pin (121) and the driver unit and the clincher unit are returned to the 0 degree position to fix.