To provide a clamp apparatus which can adjust a hydraulic pressurized fluid flow easily and certainly, having a simplified configuration for fluid flow adjustment.

The clamp body 2 of clamp apparatus 1 is provided with a fluid flow control valve 42 which can control a hydraulic pressurized fluid flow supplied to an oil room of a hydraulic pressurized fluid oil cylinder 5, wherein this flow control valve 42 has a valve port 46 which is formed in the midway of an oil path 40 and a valve element section 47a which is partially inserted in this valve port 46 at least: this valve element section 47a is provided in a clamp body 2 in a direction to approach or separate to/from the valve port 46, so as to be possible to be relatively displaced, valve element 47 is also provided, which can adjust a clearance between a valve element section 47a and the valve port 46. The flow control valve 42 has a bypass passage which makes a pressurized fluid ejected from a pressurized oil cylinder 5 to pass and a check valve.