An EGR valve includes a valve seat in a flow passage of a housing, a valve element seatable on the valve seat, a rotary shaft to open or close the valve element, a motor and a speed reducing mechanism, a return spring urging the valve element in a valve closing direction, and an opening-degree sensor to detect an opening degree of the valve element. An electronic control unit (ECU) diagnoses abnormality due to lodging of foreign matter between the valve seat and the valve element during full close. When driving the motor to urge the valve element in the valve closing direction during full close of the valve element, the ECU determines the EGR valve to be abnormal because of lodging of foreign matter if a difference between a value detected by the opening-degree sensor and a predetermined reference value is larger than a first determination value.