PURPOSE: To improve gas tightness between a rotational valve body and a valve seat part and suppress generation of abnormal noise due to gap between the rotational valve body and the valve seat part, etc., by utilizing excessive driving force of an actuator concerning an exhaust changeover valve of a diesel engine.

CONSTITUTION: A mechanism which switches reciprocating motion to rotational motion is set in connection between the output shaft 13 and the valve stem of an actuator 51, and a single or plural number of levers 1, 2 making turning movement around a position apart by a specified distance from axial line of the output shaft are arranged, and engagement members coaxially interlocked to each other are arranged on the axial line of the output shaft, and the engagement members are brought in contact with the lever in the vicinity of the stroke end of the output shaft, and thereby pressing force is applied to a valve stem by the end part of the lever. When the output shaft 13 of the actuator 51 is moved by the operation of an actuator 51, the valve stem makes turning movement in response thereto. The engagement members are brought in contact with the levers 1, 2 when the output shaft 13 reaches the vicinity of the stroke end the levers 1, 2 swing and the end parts of the levers 1, 2 are brought in contact with the valve stems so as to actuate the pressing force.