An air conditioner for performing air-conditioning of an interior of a vehicle cabin includes a casing, an evaporator, a blower, a controller, and a cooling passage. The casing defines a ventilation passage through which air flows from an air introduction port toward an air outlet. The evaporator cools the air flowing through the ventilation passage. The blower is disposed on a downstream side with respect to the evaporator in the ventilation passage and generates an airflow in the ventilation passage. The controller controls an output from the blower. The cooling passage causes a position located on a downstream side with respect to the blower in the ventilation passage to communicate with a position located on an upstream side with respect to the evaporator in the ventilation passage. A controller is installed in the cooling passage.