Abstract: An inspection apparatus for inspecting the soundness of a substrate transfer robot of a type horizontally transferring a substrate such as a semiconductor wafer mounted on a blade. The inspection apparatus is efficiently used in a multi-chamber type semiconductor manufacturing apparatus and has a noncontact type distance sensor capable of measuring a vertical distance. When the upper face of a cassette stage disposed within a load-lock chamber is assumed to be a reference surface, the distance sensor in the inspection apparatus measures the vertical distance between the horizontal reference surface and the blade of robot moving above the reference surface. From thus measured value, the warp of blade and its shaking upon movement can be detected.