A base member of a disk drive having a bottom plate, on which a spindle motor to rotate a disk is mounted, and a side wall positioned along an edge of the bottom plate. The base member has a clock window positioned on the side wall, through which a clock head to write servo track information on the disk is inserted in the disk drive, and a concave adjacent to the clock window and having a predetermined depth relative to an upper surface of the bottom plate, to accommodate the clock head inserted through the clock window.