PURPOSE: To make the forming of arrays of teeth or the impression of a traveling wave voltage on an piezo-electric element unnecessary and simplify the structure of the same, by slanting the direction of the displacement of the piezo- electric element with respect to the direction of moving a contact member.

CONSTITUTION: A piezo-electric driving device is equipped with a piezo-electric element 1 and a contact member 3 contacting the piezo-electric element 1 and movable with respect to the piezo-electric element 1. The direction of the displacement of the piezo-electric element 1 is slanted with respect to the directions A1, A2 of moving the contact member 3. When a voltage is impressed between electrodes 2a, 2b, which are in the direction of polarization, the piezo-electric element 1 is elongated and deformed while the contact member 3 is moved by the component in the direction A1 of the displacement thereof. When a voltage is impressed between the electrodes 2a, 2c, the contact member 3 moves to the direction A2.