The present invention aims to provide a compact and lightweight piezoelectric actuator, a driving method involving the piezoelectric actuator that can provide a large displacement at a low voltage, and a compact and lightweight information storage device with a high recording density that incorporates such a piezoelectric actuator and has a small moment of inertia of a head when the head is driven. The piezoelectric actuator according to the present invention has four rod-shaped driving sections. Of the four rod-shaped driving sections, a voltage is applied to the two driving sections located along a diagonal line at a time, and the voltage is applied to the two driving sections located along the other diagonal line at a different time from the time for the first two driving sections, whereby two central sections are rotationally driven relative to two end sections.