A housing has a housing main body and an outlet port. The housing main body includes a cylindrical housing inner wall that defines an internal space therein. The outlet port fluidly connects the internal space and an outside of the housing main body to each other. The valve has a valve body rotatable about an rotation axis along a rotation axis of the cylindrical housing inner wall. The valve is configured to selectively open and close the outlet port depending on a rotation position of the valve. The housing inner wall is formed such that a distance between the housing inner wall and the axis of the housing inner wall varies in a circumferential direction.