The present invention provides a disk apparatus capable of obtaining sufficient rigidity and preventing motion failure caused by deformation of a chassis outer sheath even if material having low rigidity such as aluminum alloy or magnesium alloy is used.A disk apparatus has a chassis outer sheath comprising a base body 10 and a lid 130. A disk inserting opening 11 into which a disk is directly inserted is disposed in a front surface of the chassis outer sheath, a connector 12 is disposed on the rear surface, the base body 10 is provided at its side with a discharging lever 100 which discharges the disk, the base body 10 is provided at its rear surface with a limiting lever 110 which limits the insertion of the disk, a rear base 13 is provided at a location which is not superposed on the traverse 30 and location covering a printed board 14, one of a lower surface of the discharging lever 100 and an upper surface of the rear base 13 is projected to form a discharging lever sliding surface 311 on the rear base 13, one of a lower surface of the limiting lever 110 and the upper surface of the rear base 13 is projected to form limiting lever sliding surfaces 312 and 313 on the rear base 13, and openings are formed in the rear base 13, opposite sides of the discharging lever sliding surface 311 and opposite sides of the limiting lever sliding surfaces 312 and 313.