PURPOSE: To enable the perfect retaining without destructing components, by forming a hollow part in contact part with the components, by using the facing inner surfaces of a pair of clamps, and arranging an elastic member.

CONSTITUTION: On the facing inner surfaces of clamps 11, 12, a groove 16 whose section is circular is formed. On these inner surfaces, the opening 18 of a fluid channel 17 is arranged. Elastic members 19 linking with the opening 18 are hermetically covered. A tube 20 is installed so as to be directly linked with the fluid channel 17 formed in the clamps 11, 12, and the end-portion is connected with a pressurized fluid supplying source. In the case of retaining a wafer W, an air cylinder is driven, and the wafer W is loosely retained by the clamps 11, 12. Next, from the pressurized fluid supplying source, the pressurized fluid is fed to the fluid channel 17, and the elastic members 19 are subjected to elastic expansion deformation outside the clamps 11, 12, with fluid pressure. Thereby the wafer W is pinched between the clamps 11, 12.