PURPOSE: To detect that the driving speeds of a recording medium at recording and reproduction are different each to each by detecting the distance driven in the lengthwise direction of the recording medium in a variance period of an ATF (tracking error) signal.

CONSTITUTION: The mode detection is possible by counting the number of power generation frequencies FG produced in a variance period of an ATF signal. A comparator 103 compares the ATF signal with the Vth in case the ATF signal has variance centering on the Vth. Then the number of frequencies FG are counted in a period during which the ATF signal is kept at a level lower than the Vth. If the FG is set at 720Hz in a standard time mode, 24 pulses are produced in a frame period (1/30sec). Thus it is possible to detect that the driving speeds of a recording medium at recording and reproduction are different each to each when a counter 104 counts 24 in a period during which the output of the comparator 103 is kept at L.