Embodiments of the invention improve the impact-resisting performance of a disk drive. In a head actuator assembly according to an embodiment of the invention, the difference in resonance frequency between an arm bending mode and a coil bending mode is set at a predetermined value or less. Since there is a phase difference between these two modes, an oscillation gain in the arm bending mode can be greatly decreased by approximating the two resonance frequencies to each other. Consequently, it is possible to suppress collision of a head with a recording disk caused by an external shock and thereby improve the impact-resisting performance of a disk drive.