A magneto-optical storage device having a configuration wherein a first AlN film, a Pt/co multi-layer film formed by alternately depositing Pt and Co, a second AlN film, and an Al reflective film are successively laminated on a substrate in this order. Assuming that respectively the thickness of the first AlN film is .delta.AlN (1); that of the second AlN film is .delta.AlN (2); that of the Pt single layer is .delta.Pt; that of the Co single layer is .delta.Co; and the total thickness of the Pt/Co multi-layer film is .delta.Pt/Co, each thickness of those layers is set to range within: 50 nm .ltoreq..delta.AlN (1).ltoreq.200 nm; 120 nm.ltoreq..delta.AlN (2).ltoreq.140 nm; 0.6 nm.ltoreq..delta.Pt.ltoreq.1.0 nm; 0.3 nm.ltoreq..delta.Co.ltoreq.0.6 nm; and 15 nm.ltoreq..delta.Pt/Co.ltoreq.20 nm. In accordance with the above arrangement, it is possible to greatly widen the tolerances of the film thicknesses of the first and second dielectric layers for obtaining a predetermined reflective index as well as a maximum Kerr rotation angle. Consequently, without strictly controlling the film thicknesses of the first and second AlN films, a magneto-optical storage device with stable performance suitable for practical use can be produced easily.