PURPOSE: To fix a sample on a sample mount by chucking the sample stably and securely without using an adhesive, by providing two sets of chuck members which consists of chuck claws moving by regulation screws, at the upper and the lower sides of a center pillar fixed to the sample mount.

CONSTITUTION: A center pillar 41 is fixed to a disconnection plate 142 with a screw 411, and chucks 4A and 4B are installed to the center pillar 41. Then, a fixing screw 43 is loosened, and both center blocks 42 are moved z so as to fit the interval z to the height size of a chip 2'. Then, both screw rods 44a and 44b are rotated to move x both cubic blocks 45a and 45b, and the interval x of both chuck claws 47a and 47b is fitted to the width driction of the chip 2'. Furthermore, both chuck claws are moved y by both regulation screws 46a and 46b, the chip 2' is inserted to the gap, and the both chuck claws are moved y in the reverse directions so as to chuck the chip 2'. Consequently, a random form of sample can be chucked securely.