A method of measuring a defect of a magnetic member, comprising the steps of: measuring an output from a magnetic sensor with use of an inspection probe including a magnet and the magnetic sensor which is provided on a magnetic circuit formed by the magnet and the magnetic member and which detects a density of a magnetic flux flowing through the magnetic circuit; judging whether the defect is (i) a front surface defect occurring to a front surface of the magnetic member, which front surface is a counter surface facing the inspection probe or (ii) a back surface defect occurring to a back surface of the magnetic member, which back surface is opposite the counter surface; quantitatively evaluating the defect of the magnetic member by a magnetic flux resistance computing section by applying, to an output signal from the magnetic sensor, an evaluation algorithm which is selected from evaluation algorithms set in advance for the respective ones of the front surface defect and the back surface defect and which corresponds to a result of the judging in the step; and carrying out an eddy current test of the magnetic member, in the step, whether the defect is present on the front surface or the back surface of the magnetic member is judged in accordance with a result of the eddy current test, wherein: the inspection probe includes a plurality of magnets (2, 3, 4) provided so as to form a Halbach array along a counter surface of the inspection probe, which counter surface faces the magnetic member and an eddy current flaw sensor which (i) is provided on part of a magnet provided at a center portion of the Halbach array of the plurality of magnets (2, 3, 4), which part is located on the counter surface facing the magnetic member and (ii) carries out the eddy current test; and the magnetic sensor is provided on a magnetic circuit formed by the magnetic member and a magnet that is provided at an end part of the Halbach array of the plurality of magnets (2, 3, 4), and the magnetic sensor detects a density of a magnetic flux flowing through the magnetic circuit. measuring an output from a magnetic sensor with use of an inspection probe including a magnet and the magnetic sensor which is provided on a magnetic circuit formed by the magnet and the magnetic member and which detects a density of a magnetic flux flowing through the magnetic circuit; judging whether the defect is (i) a front surface defect occurring to a front surface of the magnetic member, which front surface is a counter surface facing the inspection probe or (ii) a back surface defect occurring to a back surface of the magnetic member, which back surface is opposite the counter surface; quantitatively evaluating the defect of the magnetic member by a magnetic flux resistance computing section by applying, to an output signal from the magnetic sensor, an evaluation algorithm which is selected from evaluation algorithms set in advance for the respective ones of the front surface defect and the back surface defect and which corresponds to a result of the judging in the step; and carrying out an eddy current test of the magnetic member, the inspection probe includes a plurality of magnets (2, 3, 4) provided so as to form a Halbach array along a counter surface of the inspection probe, which counter surface faces the magnetic member and an eddy current flaw sensor which (i) is provided on part of a magnet provided at a center portion of the Halbach array of the plurality of magnets (2, 3, 4), which part is located on the counter surface facing the magnetic member and (ii) carries out the eddy current test; and a plurality of magnets (2, 3, 4) provided so as to form a Halbach array along a counter surface of the inspection probe, which counter surface faces the magnetic member and an eddy current flaw sensor which (i) is provided on part of a magnet provided at a center portion of the Halbach array of the plurality of magnets (2, 3, 4), which part is located on the counter surface facing the magnetic member and (ii) carries out the eddy current test; and the magnetic sensor is provided on a magnetic circuit formed by the magnetic member and a magnet that is provided at an end part of the Halbach array of the plurality of magnets (2, 3, 4), and the magnetic sensor detects a density of a magnetic flux flowing through the magnetic circuit.