Embodiments of the present invention provide a structure of a pivot receiving surface which may excellently adjust the attitude of a head supporting mechanism in a magnetic disk drive. In one embodiment, three projections are formed at a base for supporting a pivot assembly. The first projection is formed on a first line which bisects an angle defined between a second line and a third line determining a range, in which a head/slider flies above a magnetic disk. In contrast, the other two projections are formed at positions apart from the first projection at an angle of 120.degree., respectively. The attitude of the pivot assembly is adjusted by adjusting the heights of the projections, and thus, a head supporting mechanism is corrected in a predetermined attitude within the range in which the head/slider flies above the magnetic disk.