PURPOSE: To ensure that an inspection car runs surely on horizontal passages as well as connection stairs, by installing a crawler device each at the front and rear and at both sides of a framing on which the inspection equipment is placed and by specifying the gap between the drive and guide wheels of each crawler and the pitch of pawls furnished at external surfaces of the crawler.

CONSTITUTION: Crawler devices 1, 2 are installed on both sides of a framing 3 at the front and rear, and this framing 3 is loaded with inspection equipment consisting among others of an ITV camera 5 to constitute an inspection car for inside a container for accommodation of a nuclear reactor. Each of the crawler devices 1, 2 is furnished with a drive 12 and a guide 13 wheel at the base part and foremost part of framing 11, respectively, wound round with a crawler 14 consisting of endless belt or the like to constitute the major part. Here the gap between the two wheels 12, 13 shall be selected so that the length of the grounding part of each crawler 14 becomes equal to the length of overriding over two or more step's corners (a) in accordance with the pitch P along the slope of connecting stairs 21 formed inside the container for nuclear reactor. Pawls 16 mounted at the outside surfaces of crawlers 14 are installed at a pitch obtained by dividing the above-mentioned pitch P evenly, for ex. at a pitch of 1/2.P.