The present invention provides a heat exchanger having a heat exchanging portion HE including a plurality of paths through which a refrigerant flows and a plurality of columns of fin plate that exchange heat between the refrigerant and air, wherein, in a case where the heat exchanging portion functions as a condenser, the refrigerant is flown from a header into the heat exchanging portion HE via the plurality of paths, every two paths of the plurality of paths merge into one single path by branching/merging pipes after the refrigerant has flown through one fin plate, before the refrigerant flows through the other fin plate so as to flow out of the heat exchanging portion HE, wherein a difference in height between the highest path and the lowest path in a vertical direction is set equal to or less than half of a height of the heat exchanging portion HE.