A ventilator for performing ventilation operation to ventilate air in a living room, the ventilator comprising: an air supply fan for supplying outdoor air, as supply air, into the living room; an exhaust fan for discharging the air in the living room, as exhaust air, to outdoors; and a total heat exchanger having a supply air channel through which the supply air flows, and an exhaust air channel through which the exhaust air flows, wherein the ventilation operation includes optional ventilation operation for optionally performing ventilation, and forced ventilation operation for forcibly ventilating the living room in an amount of ventilation less than an amount of ventilation in the optional ventilation operation and greater than or equal to a predetermined required amount of ventilation, the ventilator further includes a controller for, upon receipt of a stop signal for stopping the optional ventilation operation, terminating the optional ventilation operation and starting the forced ventilation operation, and upon receipt of a start signal for starting the optional ventilation operation, terminating the forced ventilation operation and starting the optional ventilation operation, and the controller enables intermittent control for intermittently operating both of the fans (20, 21) during the forced ventilation operation, wherein airflow rates of both of the fans (20, 21) are variable, and the controller is switchable between a first operation in which both of the fans (20, 21) are continuously operated, and a second operation, characterized in that during the second operation both of the fans (20, 21) are intermittently operated by the controller at a higher fan rotation speed than in the first operation such that an amount of ventilation per unit time is substantially equal to an amount of ventilation per unit time in the first operation, thereby performing the forced ventilation operation. an air supply fan for supplying outdoor air, as supply air, into the living room; an exhaust fan for discharging the air in the living room, as exhaust air, to outdoors; and a total heat exchanger having a supply air channel through which the supply air flows, and an exhaust air channel through which the exhaust air flows, wherein the ventilation operation includes optional ventilation operation for optionally performing ventilation, and forced ventilation operation for forcibly ventilating the living room in an amount of ventilation less than an amount of ventilation in the optional ventilation operation and greater than or equal to a predetermined required amount of ventilation, the ventilator further includes a controller for, upon receipt of a stop signal for stopping the optional ventilation operation, terminating the optional ventilation operation and starting the forced ventilation operation, and upon receipt of a start signal for starting the optional ventilation operation, terminating the forced ventilation operation and starting the optional ventilation operation, and the controller enables intermittent control for intermittently operating both of the fans (20, 21) during the forced ventilation operation, wherein airflow rates of both of the fans (20, 21) are variable, and the controller is switchable between a first operation in which both of the fans (20, 21) are continuously operated, and a second operation, characterized in that during the second operation both of the fans (20, 21) are intermittently operated by the controller at a higher fan rotation speed than in the first operation such that an amount of ventilation per unit time is substantially equal to an amount of ventilation per unit time in the first operation, thereby performing the forced ventilation operation.