PURPOSE: To obtain a optical recording and reproducing device capable of accurately reproducing information by reducing the influence of shot noise, and improving the SNR of a reproduced signal.

CONSTITUTION: An outgoing light beam from an LD21 is branched to a branched light beam A and a branched light beam B by a PBS23. The branched light beam A is condensed on a recording medium 29, and a reflected light beam from the recording medium is combined with the branched light beam B at the PBS33. The intensity of the light made to interfere at the PBS33 is separately detected by the two PDs 34a, and 34b. Only a required component is fetched from the detection signal from each PD, added by an adder 36, and the level of the add signal from the adder 36 is decided by a comparator 38.