PURPOSE: To operate a piezo-electric relay efficiently by applying high-frequency voltages of different phases to piezo-electric elements of neighboring two surfaces for a specific time when the signal is ON, and applying a high-frequency voltage to a piezo-electric element parallel to the contact surface with a card, of the neighboring two surfaces of piezo-electric elements for a specific time when the signal is OFF.

CONSTITUTION: Movable contacts 5 are positioned at a constantly closed fixed contacts 6b side. And to the input signal ON, amplifiers 25A and 25B are operated for a specific time making a vibrator 1 generate a circular movement, and a card 4 is moved. As a result, the card 4 maintains a contact pressure by a friction force with the vibrator 1, and stops still. Then, when the input signal is OFF, only the amplifier 25A is operated, a high-frequency voltage is applied only to the piezo-electric element at the vertical driving side, and an opposite piece 1a oscillates bending in the vertical direction. Consequently, the still friction force inflicting the card 4 approaches zero, the card 4 is pushed by the force of a restoration spring 10 moving to the constantly closed fixed contacts 6b side, and the voltage is turned off at the time when the card 4 maintains a contact pressure. As a result, the card 4 is stopped still by the still friction with the vibrator 1, and the contact pressure of the contacts 6a is maintained.