Abstract: In a state where vibration is constantly detected, a protection function by a vibration detection circuit loses effectiveness, and thereby there may possibly arise a malfunction of an off-track detection circuit due to a pseudo-generated off-track signal. An off-track detection circuit which is capable of preventing malfunction due to a pseudo-generated off-track signal and of maintaining stable reproduction even when being under vibration, is provided by constructing the circuit not to judge as off-track when a reproduction synchronization signal is detected.