A micro-actuator of the invention includes a support frame having a base, a moving plate, a leading beam to connect the base with the moving plate; and two slider holding arms extending from both sides of the moving plate; at least one piezoelectric element bonding to the support frame to connect a free end of the base with the moving plate; wherein the moving plate sways in a first direction or in a second direction when the at least one piezoelectric element is actuated. The invention also discloses a head gimbal assembly and a disk drive unit using the micro-actuator.