An oscillator is oscillatable in a predetermined direction. First and second driving electrodes are secured to the base and apply an electrostatic force to the oscillator to make drive oscillation of the oscillator in the predetermined direction. At the time of the drive oscillation of the oscillator, a predetermined electric charge is accumulated in the oscillator, and electric charges of opposite polarities are alternately and periodically accumulated in the first and second driving electrodes, respectively, to exert an attractive force between the oscillator and a corresponding one of the first and second driving electrodes and also to exert a repulsive force between the oscillator and the other one of the first and second driving electrodes, and vice versa.