Contamination detecting device

The device of the present invention can shorten detection time by conducting contamination detection and decontamination in an identical step. Further, determination is decontamination and prevent diffusion of the a such as such as close contamination to not-contaminated portions. That is, a radiation detector is moved along the surface of an object to be detected, to detect presence or absence of contamination. A decontaminating wiping mechanism moving on the surface of the object following after the movement of the radiation detector is disposed. When contamination is detected from the output of the radiation detector, the decontaminating wiping mechanism passing the contaminated portions following after the radiation detector is operated to selectively decontaminate only the contaminated portions. As a result, the time for detection/decontamination can be shortened and diffusion of contamination such as cross-contamination toward not-contaminated portions can be prevented. (I.S.)