CONTROL VALVE

A control valve includes a casing, a valve body, and a seal cylindrical member. The casing includes an inlet and an outlet. The valve body is rotatably disposed inside the casing and includes a circumferential wall portion in which a valve hole that allows the inside and outside to communicate is formed. The seal cylindrical member includes one end portion which communicates with a downstream side of an outlet and the other end portion on which a valve sliding contact surface is provided. In the other end portion of the seal cylindrical member, a protrusion height changes continuously in a circumferential direction along a shape of an outer circumferential surface of the circumferential wall portion. A thick portion which is thicker compared to other portions is provided in a region of the other end portion of the seal cylindrical member at which the protrusion height is high.