A head actuator is made thinner without sacrificing its strength to thereby achieve the thinning of a hard disk apparatus. On the base end of each of two suspensions is provided a boss that protrudes in the direction of the side on which a magnetic head is provided, and a suspension fixing section having a hole into which the bosses are inserted is formed towards the tip of an arm. The boss of one of the suspensions is inserted into the hole from the upper end section thereof, and the boss of the other suspension is inserted into the hole from the lower end section thereof. Thus, the arm is fixed in place by being held by the two suspensions from above and below.