PURPOSE: To prevent damage for the disk and a disk device by stopping rotation while judging erroneous loading when the detected number of times for a pickup to cross a track is more than the prescribed number of times within a prescribed rotational range just after starting the loaded disk.

CONSTITUTION: When a disk 11 is loaded and a center O2 is deviated from a center O1 of a turn table 12 for Δr, a pickup 14 executes tracing in the track of a dotted line E while the disk 11 is once rotated in the direction of an arrow X. Namely, a number N of times for the pickup 14 to cross a track 25 is 4 in the order of A-D points and the A point when the deviation amount Δr is equal to a track pitch P. Therefore, the above-mentioned number N of times within the prescribed rotational range just after loading the disk 11 is detected and when it is more than a value set in advance, erroneous loading is judged to immediately stop the rotating motor. Thus, the damage for the disk 11 or the disk device can be prevented in advance.