A rotational micro-actuator (20) used in hard disk driver is disclosed. It comprises a frame (21) approximately in the shape of letter “S” and PZT pieces (28, 29) attached to said frame (21), wherein said frame (21) is formed with a central coupling portion (213) by which the micro-actuator (20) is coupled to a suspension tongue (177), and two pieces of said PZT (28, 29) are arranged in central symmetry manner about said central coupling portion (213) such that said micro-actuator (20) can rotate about said central coupling portion (213) in response to the driving signals applied to said PZT pieces (28, 29), thus cause the displacement of the head element secured to the micro-actuator (20) so as to achieve the fine positioning of the head element. With above configuration, the micro-actuator of this invention will not cause the resonance of the suspension base plate during operation. Thereby the servo bandwidth of the hard disk driver is expanded.