Piezoelectric actuator and information storage apparatus

i) Field of the Invention There are disclosed a piezoelectric actuator which can obtain large displacement at low voltage, which is small-sized and lightweight, and whose manufacture cost is low, and a small-sized lightweight information storage apparatus in which the piezoelectric actuator is incorporated, and which is provided with a small inertia moment during head driving and a high recording density. A piezoelectric actuator includes a center body and two spiral arms , and two arms are entirely in rotation symmetry and nonlinear symmetry.