a device for checking the recording state of a magneto - optical recording disk includes a detector for detecting a s - polarized light component and a p - polarized light component from a reflected light reflected from the portion of the magneto - optical recording disk . one of the s - polarized and p - polarized light components is subtracted from the other to produce a difference signal and the s - polarized and p - polarized light components are added to produce an addition signal . the difference signal is divided by the addition signal to produce a normalized detection signal . the recording state is determined based on a level change of the normalized detection signal while data is being recorded onto the magneto - optical recording disk .