A disk drive device comprises a chassis, an annular hub having an outer periphery on which a recording disk is to be mounted, and having an inner periphery to which an annular magnet is fastened, a fluid bearing unit that supports the hub in a manner freely rotatable relative to the chassis, an opposing wall formed annularly on the surface of the chassis at the hub side, and facing with at least partially the inner periphery of the hub in the radial direction, a first gap that extends in the axial direction between the inner periphery of the hub and the opposing wall, and a second gap that is continuous from the first gap and extends in the radial direction between the end face of the hub and the chassis.