PURPOSE: To provide a manipulation mechanism for a sample support member in which a sample can be safely turned upside-down and the processing of the sample can be performed from the down side as well, thereby making it feasible to deal with a variety of processings.

CONSTITUTION: A sample support member 1 is constituted of a platform 2 for fixing a sample 20 and a stub for supporting the platforms 2 and has a groove 4 to insert a fork. A post 9 is fitted into the space 3c of the stub, and the hook part 5b of a pair of lock levers 5 is inserted into the part 9c of small diameter of the post with a twisting coil spring 7, so that the sample support member 1 is locked into the post 9. A fork 8 is inserted into the fork inserting groove 4, and when lock lever abutting surfaces 5a are pressed by the fork 8 to come close to each other, the lock levers 5 fluctuate with the center 6 of fluctuation acting as a fulcrum and the hook part 5b is opened to release a lock. Thereby, since the lock and the release action are performed by making with the movement of the fork, they can be operated by one- touch, so that the structure is simplified. Also, even when the sample support member comes apart from the post, the fork is inserted into the fork inserting groove to support the sample support member, and therefore, even when the fork is rotated by 180° to turn the sample support member upside-down, it is not fallen off.