PURPOSE: To provide a low cost, highly precise tool that needs not be exchanged according to a sample size by a structure wherein the sample is inserted into a movable mechanism.

CONSTITUTION: The 1st contact area 16 provided in a groove equipped under a 1st member 11 comes in contact with part of the upper surface and part of the side, of the 1st sample 5, while the 2nd contact area 17 provided in a groove equipped under a 2nd member 12 comes in contact with other part of the upper surface and other part of the side, of the 1st sample 5. A movable screw 13 is rotated, the member 12 is moved toward the member 11, the sample 5 is brought into contact with the contact areas 16, 17 and held between them. The movable screw 13 is rotated according to the sample 5 size, moved from or to the member 12 and the fitting portion is expanded or contracted to clamp the sample 5.