In this paper, we report on the development and evaluation of an inspection system prototype for inspection of an inner wall of a large boiler. A sensing vehicle, ground equipment and a ground console were prototyped. The vehicle has a horizontal slider table for wide-range scanning by a distance image sensor. A vibration suppression mechanism reduced the inertial force during slider movement. Two winches with automatic locking mechanism for climbing and a laser displacement meter for altitude measurement were installed as ground equipment. In addition, operating software for the inspection system prototype was developed, and this enabled exchange of measurement data and transmission of commands between the vehicle and the console. We also realized autonomous wall climbing of the vehicle while remaining level. Evaluations on a large imitation wall were carried out and they confirmed successful autonomous wall climbing and remote scanning.