A HDD includes a disk unit, a circuit board and an air intake and exhaust mechanism. In the disk unit, a magnetic disk is rotatably provided. The circuit board is provided with a driving circuit including electronic components. The air intake and exhaust mechanism includes a bag provided between the disk unit and the circuit board. The bag includes a communication hole airtightly communicating with an air intake and exhaust hole provided in a housing of the disk unit, and air intake and exhaust valves are provided at the bag, and located apart from the communication hole. Due to this structure, when the internal air pressure of the disk unit changes, gas flows into and out from the gap between the disk unit and the bag through the communication hole, thus restricting changing of the air pressure.