PURPOSE: To easily find out a defect of a journal part of a crank shaft.

CONSTITUTION: An inspector 10 is provided with a body 11 with a guide face in contact with a journal part 4 of a crank shaft, an operation part 12 provided on the body 11 and a sensor means 14 having a probe 13 and the like. A guide face 20 is made a circular arc recess face of an inside diameter in accordance with the outside diameter of the journal part 4, and the distance from the center C of the journal to the edge 30 of the probe is kept constant over the entire circumference of the journal part 4 by engaging the guide face 20 with the journal part 4. The thickness of the body 11 is equal to the length of the journal part 4 and the body 11 engaged with the journal part 4 is provided so that it may not be moved axially. Eddy current is generated in a fillet part, and the probe 13 detects a signal in response to its electromotive force and is connected to a signal processor 16 through a signal cable 15.