PURPOSE: To measure the coercive force distribution of a photomagnetic recording medium in a short time by using magnetic field applying elements arranged across the photomagnetic recording medium and measuring the coercive force by utilizing the magnetooptic effect of light converged by a cylindrical lens.

CONSTITUTION: The photomagnetic recording medium 19 is moved by a rotating machine 21 in a magnetic field established with the magnetic field applying elements 15 and 16. On the other hand, laser light which is converged by the cylindrical lens 14 and sectioned elliptically is made incident through a half- mirror 5 and reflected laser light or transmitted laser light under the influence of hysteresis-free magnetooptic effect corresponding to the coercive force of the medium 19 which varies according to the long-axis position of the ellipse is photodetected by a photodetector 17 or 23. The magnetooptic effect which does not draw a hysteresis curve eliminates the need to stop the medium 19 and apply a low-frequency alternating magnetic field, and the coercive force distribution of the photomagnetic recording medium is measured in a short time.