PURPOSE: To improve the response of speed detection of an optical spot by allowing a speed detection circuit detecting the moving speed of the optical spot to the optical disk to detect the moving speed of the optical spot plural number of times during one track pitch.

CONSTITUTION: Track crossing optical information of the optical disk is given to an optical detector, an RF signal corresponding to one track pitch is inputted to a comparator 51, where the signal is converted into a rectangular wave signal S2. The signal S2 and an output signal S3 of a reference clock pulse generating circuit 52 are inputted to a logic circuit 1. An output signal S6 of the circuit 1 is formed corresponding to the 1st period with a rectangular wave signal and the 2nd period not in existence and an output of an AND circuit 54 is fed to a counter circuit 55. The count counted at each open period is stored in a storage circuit 57 by a holding signal S9 and a setting signal S12 from the circuit 1 and the circuit 57 outputs a speed data having an inverted level of the count as a digital signal. Thus, the detection is applied twice for one track pitch to improve the response.