A coolant-control valve that performs initialization learning using a stopper and provides an efficient structure by an initialization learning stopper within an actuator which drives a valve body. The coolant-control valve is equipped with a rotor driven to control a flow rate of coolant for cooling an engine, a casing that houses the rotor, and a rotary drive device that drives the rotor. Control means of the rotary drive device have an initialization learning function of an operating range of the rotor. The rotary drive device is equipped with a motor and a reduction gear. The operating range of the rotor is restricted by the operating range of an output gear among power transmission elements in the reduction gear. A groove of the output gear and a fixed-angle stopper inserted into the groove are restricting means for use during initialization learning by the control means.