PURPOSE: To scan and inspect the flow passage of a narrow part, having a complex curved surface, accurately by installing an arithmetic controller, having a logical function of storing reference measurement data of the flow passage surface of a water wheel, between a car truck controller and a recorder.

CONSTITUTION: A running car truck 2 mounted with a TV camera 5 is provided an oscillating device 8 with a probe 7, a control detector 6 for the profile of an arm wall surface, a distance measuring instrument 9, and an arm angle detector 10, and they are connected to an arithmetic controller 15. For the nondestructive inspection of the flow passage I of a pump water wheel, when the running car truck 2 is run on the flow passage I, detection signals from the control detector 6, probe 7, distance measuring instrument 9, and arm angle detector 10 are sent to the arithmetic controller 15 to be operated, and consequently the movable arm 3, etc., of the running car truck 2 are controlled through a car truck controller 14 to record the data in a storage device at the same time.