A magneto-optical recording/reproducing apparatus which comprises a first optical system (1) provided with a first objective lens (2), a second optical system (21) provided with a second objective lens (22) having a numerical aperture different from that of the first objective lens, and a magnetic head (19) that is provided close to a magneto-optical recording medium for recording and is driven together with the second objective lens (22) in a body. Even when either of a first and a second magneto-optical recording medium (41, 42) having recording densities different from each other is loaded in the magneto-optical recording/reproducing apparatus, the recording or reproducing thereof is possible. Therefore, the compatibility between the first and the second magneto-optical recording medium (41, 42) is obtained.