To provide an instant protection method capable of suppressing an overcurrent from being generated in a voice coil motor used in an optical disk machine.

In this method, in (A) process, a digital signal processor DSP executes a voice coil motor protection module at prescribed time intervals and in (B) process, the DSP executes following processes by executing the voice coil motor protection module. Namely, in (b1), the DPS reads the signal value TE of a tracking error and the signal value FE of a focus error and judges whether the TE and the FE exceed a safety extent value or not and (b2) when frequency in which the TE and the FE of the process (b1) exceed the safety extent value exceeds a 1st prescribed value, the DSP decreases a control current to be outputted to a voice coil motor by lowering the gain work of a signal amplifier and (b3) when frequency in which the TE and the FE of the process (b1) exceed the safety extent value exceeds a 2nd prescribed value, the DSP starts up multiplied speed decreasing work and controller current lowering work. Thus, this method assures the safety of the voice coil motor.