To enable easily and surely approaching structures having curvature in an narrow space and hold an inspecting component and inspecting object surface in a certain contact state by providing a mechanism which is freely attachable/detachable to incore structure, and is for moving the inspecting component and approaching the inspection object position.

The base 4 of incore structure inspection device body is hung down between a reactor pressure vessel 101 and for example, core shroud 102 outer surface and a support arm 9a for extending is extended upward with an air cylinder 10a to extend the vertical gap of wheels 5a and 6a and positioned at the outer periphery of shroud middle part 102c. Then, the vertical gap of the wheels 5a and 6a is shortened to pinch the upper surface of the shroud upper ring 102b and lower surface of a middle part ring 102b. Next, if a guide roller 25 is pushed to the inner periphery of the pressure vessel 101 with an air cylinder 25a, a probe 13 fixed to a mount 12 movable upward and downward softly touches the outer periphery of upper shroud 102c. By driving 7a and 8a the wheels 5a and 6a for running, wide range scanning of the outer surface of the upper shroud 102c is possible.