PROBLEM TO BE SOLVED: To provide a flaw detector capable of realizing high precision flaw detection by making the magnetic flux density of measurement region high resolution by detecting the change of magnetic flux density by changing the rotation angle of polarization surface using the Faraday effect, in the case of detecting the flaw in a member under testing of magnetic substance. SOLUTION: The flaw detector comprises: the coil 1 for making flow an eddy current in the member under flaw test 2 of magnetic substance for generating alternative magnetic field; the magnetooptical element 3 with a reflective film disposed at the tip opposite to the surface of the member under flaw test 2 is arranged at the center of the internal periphery of the coil 1; the optical fiber 4 for making light from the light source 5 enter the magnetooptical element 3 through the circulator 9 toward the reflection film; the optical fiber 4 for making the reflected light reflected by the reflection film enter the analyzer 10 through the circulator 9; the photoelectric transducer 11 for transducing the output light of the analyzer 10 into an electric signal; and the operation processor 12 for detecting the flaw of the member under flaw test 2 by processing the output signal of the photoelectric transducer 11 based on the rotation angle of the polarization surface of the reflected light. COPYRIGHT: (C)2006,JPO&NCIPI
