The present invention relates to an air conditioner for a vehicle, which takes up less installation space due to its compact-sized structure and effectively performs cooling and heating with a simple structure. The air conditioner for a vehicle includes: a case (10) having an air inflow port and an air outflow port; a blower for introducing air into the air inflow port to send the air into the case (10); a compressor (30) for compressing refrigerant; a heat exchanger for exchanging heat between refrigerant and air; and an expansion means for throttling the refrigerant, wherein the blower, the compressor (30), and the heat exchange are arranged inside the case (10) side by side to be formed in a flat type.