PURPOSE: To improve management in case of use by providing a manual control circuit and an automatic switch circuit interlocking with a heat source such as a gas instrument, operating the ventilating fan with an electric shutter by turning one circuit ON and stopping the fan by turning both circuits OFF in the ventilating fan.

CONSTITUTION: When a water heater 8 is not operated, an automatic switch circuit 7 is not conducted, and relay switches 16, 18 are brought to opened states and a relay switch 17 to a closed state. when a manual switch 4 is operated under the state and a movable contact piece 4a is connected to fixed contacts 4bW4e, motors 1, 3 are conducted, and the fan and the shutter can be driven. When the water heater 8 is ignited, a relay 13 is conducted through the automatic switch circuit 7, the relay switches 16W18 are changed over, the motors 1, 3 are operated, and the fan and the shutter are driven. They are driven even when the switch 4 is at OFF at that time. According to the constitution, air can be ventilated manually even when the water heater is not being used.