A disk drive device includes a recording medium, a head slider having a head element for recording data on the recording medium and for reading data recorded on the recording medium, a spindle motor for rotating the recording medium, and a clamp for applying a pressing force to the recording medium to fasten the recording medium to the spindle motor. The disk drive device has a feature in which a film body formed from a material which is more pliable than a material forming the clamp is interposed between the clamp and the recording medium. Even if the clamp does not have a high flatness, the film body absorbs irregularities of the clamp. Thus, it is possible to fasten the recording medium with the clamp while apparently keeping flatness.