An engine, an intake passage to introduce intake air to the engine, an exhaust passage to discharge exhaust air from the engine, and a high-temperature duct connected to the intake passage to introduce high-temperature air around the exhaust passage into the engine are provided in an engine compartment. The intake passage includes an intake-air inlet port to introduce outside air as low-temperature air. A passage switching valve provided between the intake passage and the high-temperature duct switches passages of the high-temperature air from the high-temperature duct and the low-temperature air from the intake air inlet port so as to selectively flow the air downstream of the intake passage. A valve control unit controls switching according to the temperature inside the compartment.