A heat exchanger of an air conditioner comprising: at least one or more refrigerant inlets for connecting a compressor for compressing refrigerant to an expansion device for expanding condensed refrigerant via a piping and for receiving high temperature/pressure refrigerant coming from the compressor via a four-way valve; at least one or more refrigerant outlets for discharging the refrigerant to the expansion device, wherein the number of the refrigerant outlets is greater than that of the refrigerant inlets, such that same performances can be achieved for both the cooling and heating purposes albeit the heat exchanger being simplified in the structure thereof, and manufacturing cost can be reduced to thereby improve the productivity.