The present invention provides a flaw detector for wire rope, which can less maintain the pushing force relatively to the radial direction of wire rope and can restrain the vibration of the wire rope. The flaw detector comprises the following components: a pair of permanent magnets (2a,2b) which perform magnetization in the length direction of the wire rope (4); a magnetic sensor (3) which is configured near the part of wire rope (4) magnetized by the permanent magnets (2a,2b) for detecting the leakage flux leaded from the magnetized part of the wire cable (4); and a pair of positioning mechanisms (5,6) which are used for positioning the permanent magnets (2a,2b) and the magnetic sensor (3) relatively to the wire rope (4). Each of the positioning mechanisms (5,6) comprises the following components: rotating members (5a,5b,5c,6a,6b,6c) which contact with a mode of surrounding three respective positions on the periphery of the wire rope (4); and spiral springs (5d,5e,6d,6e) which cause the rotating members (5a,5b,5c,6a,6b,6c) to generate compact contact forces relatively to the wire rope (4).