A magnetic disk drive apparatus includes a housing member with at least one opened face, a cover member for covering the at least one opened face of the housing member, a head gimbal assembly including a magnetic head slider and a suspension for supporting the magnetic head slider, a support arm for supporting the head gimbal assembly, a magnetic disk to which the magnetic head slider opposed, and a motor for rotating the magnetic disk. The magnetic disk and the motor are attached to the housing member. The support arm is fixed to the cover member using a clamping hole formed through the cover member. The cover member has a local deformation structure that is capable of locally deforming and formed around the clamping hole.