In order to realize reduction in thickness of a disk device including a turntable and a clamper in which a disk is mounted on the turntable and pressed and clamped by the clamper by reducing height of the clamper, the clamper is constituted with a clamper body integrally formed of synthetic resin, a magnet, and a clamper plate made of a metal magnetic substance. The clamper body has a disc-like clamp section to press the disk, a cylindrical center guide forming a housing space for the magnet in a center thereof, a cylindrical outer ring erected from the clamp section, and locking pieces extending to inward from an upper part of the outer ring so as not to project over an upper end of the outer ring and an upper end of the center guide and being arranged at equal intervals in two or more places. The clamper plate has hooks extending below to engage with the locking pieces respectively.