PURPOSE: To circulate coolant to cool the center part of the main body of a piezoelectric device actuator without requiring a pump, etc., by a method wherein a first linkage path is provided on the upper end side of the main body and a second linkage path is provided on the lower end side of the main body and a coolant circulation path between the inside space of the main body and around the outer circumference of the main body.

CONSTITUTION: The inside space 15 of the main body 1 of a piezoelectric device actuator is composed of the inner holes of respective piezoelectric devices 1a. The inside space 15 and the predetermined space 3 outside the main body 1 are linked with each other by the first linkage path 5c of a first shim 5 and the second linkage path 6c of a second shim 6. A circulation path through which insulating oil in the inside space 15 is circulated and returned to the inside space 15 is composed of the first linkage path 5c, the predetermined space 3 and the second linkage path 6c. Two valves 11 and 12 which can be opened in the direction of the circulation are provided in the circulation path. If heat is generated in the main body 1 of the piezoelectric device actuator, the insulating oil is circulated by the expansion and contraction of the main body 1 and the center part is cooled to make the temperature distribution uniform.