A magnetic disk device having a cover of a simple structure having high
rigidity and not easily deformable by pressure from the outside. An
envelop surface configuration (46) of at least a portion of a cover (40)
positioned opposite a magnetic disk (2, 43) is made generally conical,
such that the distance from the magnetic disk decreases along a direction
from the vicinity of a rotating shaft of a motor, as the center, toward
the outer periphery of the magnetic disk, thereby reducing the amount of
deformation of the cover, particularly in the vicinity of the rotating
shaft of the motor.