PURPOSE: To provide a sample holder having a simple structure and capable of invariably holding the sample face at the same height for samples different in size and thickness.

CONSTITUTION: A sample base 12 provided with three stanchions "2a having round tips is vertically movably provided at the center of a sample holder base material 11. The sample base 12 has a rack gear 13 extended downward. The rack gear 13 is meshed with a pinion gear provided on a motor 15 controlled by a microcomputer 10. Two butt pins 4 are provided at the center angle of 120° on the periphery centering on the sample base 12. A release lever 3 movable in the approaching/separating direction to or from the sample base 12 is provided on the opposite side. The release lever 3 is excited toward the sample base 12 by a spring 2. The inside end is forked, and a pressing pin 1 is provided.