PURPOSE: To eject automatically a defective disk when the increment value of a prescribed counter exceeds a prescribed level by increasing the value of said counter by the sound jumping frequencies which occur at the same position for each of continuous tracks during reproduction of disks.

CONSTITUTION: The positions on each track can be detected from the index numbers, etc. contained in the tracks within a program area PA. Thus a flaw 101 is identified from a flaw 102 to measure these flaws at the same position for each circulating track. The values of counters corresponding to the flaws 101 an 102 are increased successively at positions corresponding to each track. It is decided that the reproduction is impossible for the degree of a fault when the count value of one of both counters exceeds a prescribed count value N. Thus a defective disk is detected. When a defective disk is decided, the reproduction is discontinued. Then an alarm is given to a user by means of a lamp or buzzer tone. At the same time, a DAD is ejected and the power supply is cut off.