PURPOSE: To prevent the occurrence of an abnormal sound in a gap between the external surface of a valve plate and the internal surface of a housing, regarding a rotary solenoid type actuator used as a valve for controlling the flow rate of fluid via the turning of the valve plate.

CONSTITUTION: A housing 11b having an air inlet 11a and an air outlet 11b is provided therein with a drive shaft 12 and a valve plate 15 turned thereby for opening and closing the outlet 11b. The valve plate 15 has a valve plate body 15a formed by cutting out a cylindrical member along an axial direction, and the divisional member 11c of the housing 11 is so formed as to have internal surface 11d faced to the external surface 15c of the body 15a. The internal surface 11d is fitted with a seal member 40 and the end thereof is in pressed contact with the external surface 15c of the valve plate 15. According to this construction, an air flow in a gap 30 between the internal surface 11d and the external surface 15c is completely interrupted, thereby preventing the occurrence of an abnormal sound.