PURPOSE: To perform smoothly the inspection works in a narrow space by connecting an auxiliary unit removably to a manipulator through a stabilizer attached to the proximal end face of the n'th joint shaft of the manipulator and furnishing a driving mechanism for self running on the auxiliary unit.

CONSTITUTION: To inspect a narrow space, an auxiliary unit 17 connected electrically with a manipulator 1 through a cable 16 is integrated with the manipulator 1 through a stabilizer 15 installed on the proximal end face of the n'th joint shaft 1d of the manipulator 1 and is intruded into the narrow space by a driving mechanism. Then the auxiliary, unit 17 is disconnected from the stabilizer 15 and also separated from the manipulator 1, and the desired inspecting works are conducted. At this time, the manipulator 1 and auxiliary, unit 17 are moved by their respective driving mechanisms for self running furnished on them.