Abstract: In an optical disk device, an output terminal is connected to an optical pickup, and a preceding sub-beam returning light signal which is electrical signal obtained by converting returning light of a sub-beam preceding an main beam is output through the output terminal. A defect period detection circuit detects a defect period during which a beam is passing through a defective portion on an optical disk based on the preceding sub-beam returning light signal from the output terminal. A servo hold circuit holds tracking servo during the detected defect period. Therefore, even when an amplitude of an RF signal is quickly attenuated during the defect period, the defect period is detected at an early stage of the attenuation, thereby suppressing a change in an amplitude of a tracking error signal to a small level.