To provide a revolutionary bending device capable of simply bending a plate material with power, easily performing bending/holding by switch operation of a gripping finger and upward movement while holding without applying force, easily drooping/bending without over-extending a body in a high place worker and significantly improving working efficiency with safety.

To the tip part of a portable actuation device A, in which by actuating an operation switch 2 arranged at a fingering position of a gripping part 1, a pressure medium of air, oil, etc., is pressure fed through a valve mechanism to a cylinder device in a main body part 3 continuously arranged at the gripping part 1 to actuate an actuation rod 6, a plate material holding device B to open/close by actuating the actuation rod 6 is arranged, at the state the end part of the plate material 7 is held by the plate material holding device B, by turning the actuation device A in a prescribed direction, the plate material 7 is bent.