Abstract: Opposed faces of two disk substrates are bonded by an adhesive layer whose characteristic parameters are set in predetermined ranges, particularly in the values of a product of Young's modulus and the film thickness in a range of 1.0.times.10.sup.-2 kg/mm to 3.0 kg/mm, a product of Young's module and the thermal expansion coefficient in a range not larger than 1.5.times.10.sup.-2 kg.multidot.mm.sup.-2 .multidot..degree. C..sup.-1, or a product of the thermal expansion coefficient and the film thickness in a range not larger than 2.0.times.10.sup.-5 mm /.degree. C. Preferably, the glass transition point of the used adhesive is set to a value in a range of 20.degree. C. to 80.degree. C., and the film thickness is set to a value in a range of 10 .mu.m to 100 .mu.m.