Embodiments of the invention prevent contact between a peripheral edge of a magnetic disk and a counter surface of a ramp when the magnetic disk is displaced. In one embodiment, a ramp is disposed near the peripheral side surface of a magnetic disk. The ramp has magnetic disk retainers each having slide surfaces and counter surfaces respectively facing the recording surfaces of the magnetic disk. Grooves or recesses are formed in the counter surfaces to define relief spaces. When the peripheral side surface of the magnetic disk is displaced toward the counter surface by shocks exerted on the magnetic disk drive, the relief space prevents the peripheral edge from coming into contact with the counter surface. Thus the amount of particles produced by the collision of the magnetic disk with the ramp can be reduced.