PURPOSE: To prevent effectively stylus skips, by controlling the position of a light spot after detecting a signal which discriminates a flaw on a recording medium out of a sum signal existing at a prescribed area of a photodetector.

CONSTITUTION: The output signal of an information signal extracting/arithmetic circuit 25 is transmitted through an LPF33 and contains no information signal component nor error signal component to have a small degree of variation. The circuit 25 and an LPF33 constitutes a sum signal extracting circuit 35 for detection of flaws. If a disk contains some flaws, the total light quantity has a fluctuation with a large pulse emerging at the output of the LPF33. A level deciding circuit 34 decides a flaw when a pulse higher than a prescribed level is detected and then delivers a flaw detecting signal. The output of this detection is connected to a control input of focus and tracking error holding circuits 31 and 32, respectively. Then the error signal delivered immediately before detection of a flaw is held at a moment when the flaw is detected. Therefore, it is avoided that the focus or tracking error signal is deflected due to the presence of flaws. This device reduces greatly the generation of stylus skips.