It is provided a drive unit 1 in which the displacement amount of the frictional engagement member 7 can be reduced without lowering the driving torque, having a drive circuit 4 comprised of a bridge circuit which includes charge switching elements Q1, Q3 for connecting the electrodes 5a, 5b of the piezoelectric element 5 to the power supply 2 and discharge switching elements Q2, Q4 for connecting the electrodes 5a, 5b to ground, and a switch circuit 9 for inserting a limiting resistor R2 in at least either one of an current path between the power supply 2 and the piezoelectric element 5 and an current path between the piezoelectric element 5 and the ground.