A storage device includes a partition wall dividing an interior of a casing into a disk chamber and a drive chamber. Recording disks are rotatably disposed in the disk chamber. Arms, each supporting a read/write head at a distal end portion thereof are capable of exteding into the respective spaces between the recording disks through an opening of the partition wall. An actuator is mounted within the drive chamber for linearly reciprocating the arms to cause the heads to skim across recording surfaces of the recording disks. An interrupting surface is formed on a portion of the partition wall at a downstream side of the arm with respect to an air flow due to the rotation of the recording disks, for interrupting the air flow to convert a dynamic pressure of the air flow into a static pressure thereof. With this arrangement, the air is prevented from flowing back from the drive chamber into the disk chamber.