Embodiments of the invention provide a magnetic disk drive that allows members to be mounted onto a base simply and accurately. In one embodiment, a magnetic disk drive comprises: a base; a disk assembly including at least one magnetic disk and mounted rotatably on the base; and an actuator assembly including at least one actuator having a magnetic head and mounted swingably on the base. The base is formed with a guide. The guide functions to guide, when a member to be disposed on the base is to be mounted, the member from a corresponding initial placement position of the member on the base to a target position, at which the member is to be disposed. Further, the guide includes a positioning portion, against which the member abuts at the corresponding target position.