A magnetic disk apparatus can achieve reduced thickness by reducing thickness of the clamp, improved shock resistance achieved by an increase of clamping force, and reduced rotating synchronous deviation due to such as camber or undulation of a disk generated by eccentricity of the disk depressing section, a disk receiving surface of the spindle hub and the disk. That is, on a circumference more inwards than a portion in contact with an outside diameter of screw head section and clamp, clamp has displacement section in a screw axial direction throughout the whole circumference with a contact section set as a reference.