To provide a holding device for peripherally holding workpiece of any desired outline.

This holding device comprises two shape-adjustable jaws 26 provided opposed to each other at a body 11. The grip surfaces 32 of the jaws 26 are composed of a plurality of plungers 33 independently movable to a workpiece by fluid power and stoppable in the workpiece holding position. The body 11 is rotatably supported on a grip device 10 in order to rotate around an axis vertical to a workpiece holding direction, and has a connecting member 75 for fluid power operation of fluid power drive of the plungers 33. A connecting member 76 connected to a fluid power path is further provided to press the connecting member 75 and is fittable at a specified angle to the body 11 in the stationary state of the body 11. The body 11 has a valve means for locking the positions of the plungers 33 in the clamping state even after separating the connecting member 76.