PURPOSE: To make a magneto-optical recording/reproducing device suitable for a use in combination with an magneto-optical recording carrier provided with a pre-arranged hole-structured section mark and to make it possible to avoid a generation of an unwanted transient phenomenon in an output of a selection circuit even at a high radiation level.

CONSTITUTION: A radiation source 4 to make a magneto-optical recording/ reproducing head generate a radiation beam 5 is provided, and the radiation beam is focused on a magnetooptical detection system 7 by an optical system 6 via a record carrier 1. The magneto-optical detection system 7 is provided with a radiation induction detectors 10 and 11, and their detected outputs are led to inputs of adder circuits 13 and 14 via coupling current-voltage converters 12 and 15 to obtain the sum and difference of the signals. The summed signal of the outputs of the adder circuit 13 is led to an input 20 of a selection circuit 17 through a capacitance coupling 16, while the differential signal of the outputs of the subtracter circuit 14 is led to an input 22 of the selection circuit 17 at the same time, and an output 21 is led to a signal processing circuit 18a through a capacitance coupling 18.