AIR CONDITIONER

PROBLEM TO BE SOLVED: To provide an air conditioner for a vehicle that can reduce energy consumption during the pre-air conditioning and improve heating performance.SOLUTION: The air conditioner comprises: an air conditioning unit 125 including a heat pump; an outside air temperature sensor 331 for detecting the outside air temperature of a vehicle; an inside air temperature sensor 332 for detecting the air temperature inside the vehicle; and an ECU 300. The ECU 300, when an operating time of the air conditioning unit 125 reaches a set time, the inside air temperature detected by the inside air temperature sensor 332 reaches the set time or power consumption of the air conditioning unit 125 surpasses an acceptable amount, stops the air conditioning unit 125. The ECU 300, when the outside air temperature detected by the outside air temperature sensor 331 during heating is less than a limiting temperature for heating capability of the heat pump, activates an engine.