Embodiments of the invention provide a head gimbal assembly and a head stack assembly suitable for a miniature magnetic disk drive, and capable of being assembled in an accurate alignment during its fabrication. In one embodiment, a fixing member is disposed in contact with a pivot, an assembly formed by combining a head gimbal assembly and a carriage assembly is put on the pivot and pressed in the direction of the arrow toward the fixing member, and is fastened to the pivot with a nut. Since the head gimbal assembly is provided with a hole to receive the pivot therein provided with two straight edges, the relative positions of the turning axis of the pivot, the head gimbal assembly and the carriage assembly are adjusted properly so that clearances between the parts are absorbed.