The present invention relates to an automatic retrieval method of a wavelength-division multiplexed (WDM) ring network to the normal state after recovery of a failure. More specifically, the present invention relates to an automatic retrieval method of a WDM ring network to the normal state after recovery of a failure by inducing a lasing by making the gain of the closed loop larger than 1 using the fact that the recovered section in the ring network forms a closed loop immediately after the recovery of the failure.