Embodiments of the invention establish electric continuity across an actuator head suspension assembly and a pivot bearing assembly without involving an increased manufacturing cost through a simple structure. In one embodiment, a carriage made of a plastic resin is provided with a pivot opening. A pivot bearing assembly is inserted into the pivot opening. The pivot opening includes a step formed by holes having different hole diameters from each other at an adjoining portion thereof. Two actuator arms are secured to the carriage through insert molding to support an HDA. One of the two actuator arms is provided with a hole functioning as a pivot opening and having a smaller hole diameter so as to form the step. The other of the two actuator arms is provided with a hole functioning as a pivot opening and having a larger hole diameter. The hole having the larger hole diameter includes protruded portions that abut against the pivot bearing assembly with no clearance therebetween. The hole also includes recessed portions disposed between each adjoining pair of the protruded portions and having a clearance from the pivot bearing assembly.