PURPOSE: To prevent the fluctuation of a DC level and to smoothly execute searching operation by detecting the boundary between a recorded area and an unrecorded area based upon a peak value detecting signal, discharging electric charge accumulated in a coupling capacitor.

CONSTITUTION: When an optical pickup approaches the boundary between a recorded area AW and an unrecorded area NW at the time of searching operation, an RF component is not included in an RF signal A in the succeeding area NW. Thereby, a single amplitude waveform is formed, a difference between a peak value VP and a bottom value VB disappears, the output of a peak value detecting circuit 5 comes to approximately equal to that of a bottom value detecting circuit 6, and a comparator 7 outputs a reset pulse E. Thereby, a reset circuit discharges the charge accumulated in the capacitor 2 and a corrected detection signal D is obtained. Consequently, a difference between the reference levels of the areas AW, NE is not generated and an on-track detection signal C to be the output of a comparator 4 comes to an accurate track counting pulse, the generation of miscounting can be prevented, and smooth searching operation can be executed.