A Head Gimbal Assembly (HGA) of the invention includes a slider; a micro-actuator to adjust the position of the slider; and a suspension to support the slider and the micro-actuator. The micro-actuator includes two side arms; a load plate for supporting the slider, which is connected with at least one of the side arms; a pair of piezoelectric (PZT) elements connected with the side arms; and a support shaft coupled with the suspension, the support shaft being connected with the side arms and positioned between the PZT elements. The invention also discloses a disk drive unit using such a HGA.