An optical disk device for discriminating the kind and the insertion status of an optical disk with a simple mechanism so that it can unload the optical disk in case something is wrong. When the loading of the optical disk (12) recorded with information is started, a pair of rollers (14, 14) are rotated to clamp the optical disk (12) inserted into the slot (11) of the body (13) of the optical disk device (10) and load the disk into the inside of the body (13). At this time, circumferential edge detection means (20) disposed in the body (13) continuously detects the circumferential edge (12a) of the optical disk (12) inserted, so that it detects the external diameter, shape and insertion status of the optical disk (12) inserted. In case something wrong is judged, the optical disk (12) is unloaded.