Abstract: The invention provides an improved contamination inspecting device which can carry out continuous, automatic inspection of portable articles both large and small regardless of their shape. The device incorporates a conveying means for carrying the articles through the inspection position wherein the speed of the conveying means is varied based on the background radioactivity detected by the plane scintillator, a plane scintillator for detecting radiation from both the background environment and the articles to be inspected, a five-axes gate-type underriding mechanism which incorporates a robot arm so as to enable the plane scintillator to travel along the surfaces of each article, and control means for controlling the speed of the conveying means based on the background radioactivity detected by the plane scintillator and for controlling the five-axis robot based on the shape of the articles to be inspected.