PURPOSE: To positively detect abnormal access to a radiation source by a sample regardless of the irradiation direction of an X-ray source to an object to be inspected.

CONSTITUTION: This device applies a radiation from a radiation source 1 to a sample S to be inspected which is retained at a sample holder 11 and then detects the sample image according to the radiation transmittance using a radiation sensor. Then, access monitoring means 13, 15, etc., for detecting access of the sample S to the radiation source 1 exceeding a specific distance are provided in one piece with the sample holder 11 so that they can be moved.