PURPOSE: To correctly detect a defect position and to improve a reproducivility of an inspection, by a method wherein an index sheet is adhered to a surface to be inspected, and a defect finding head, incorporating an ultrasonic probe and an index mechanism, is movably attached.

CONSTITUTION: A thin filmform index sheet 3, which is made of an ultrasonic permeable material and has a position detecting optical index 4 at its surface, is adhered to a part covering a weld 2 of a lining 1. A defect finding head 5 is constituted such that it moves in a peripheral direction along the surface of the index sheet 3 togetherwith a moving object 10, and slides in an axial direction togetherwith a defect finding lever 14. An ultrasonic probe 18 and an index detecting mechanism 21 are located in the defect finding head 5. The head 5 is constituted such that the index sheet 3 is irradiated with a light from a lamp 22 and a reflection light is caused to enter a photo detector 24, and this causes defecting of the index 4 and the position of the probe 18.