An outdoor unit of an air-conditioning apparatus, comprising: a heat exchange body including a plurality of flat tubes that extend in a vertical direction and are arranged in a horizontal direction with gaps therebetween, wherein a plurality of the heat exchange bodies are arranged in a direction of air flow to form a heat exchanger , and wherein a first header , into which hot gas refrigerant flows from a refrigerant circuit, is provided below one of the plurality of the heat exchange bodies that is at a most upwind position, characterised in that a refrigerant distributor having a double-pipe structure is provided below one of the plurality of the heat exchange bodies that is at a most downwind position, the double-pipe structure including an inner pipe having a plurality of refrigerant holes through which refrigerant flows and that are arranged with gaps therebetween, and an outer pipe into which the inner pipe is inserted, and wherein the heat exchanger has a refrigerant flow passage along which, when the heat exchanger functions as an evaporator, the refrigerant flows into the one of the plurality of the heat exchange bodies that is at the most downwind position through the refrigerant distributor and flows out of the one of the plurality of the heat exchange bodies that is at the most upwind position so that the refrigerant and air flow in opposite directions, wherein each of the first header and the refrigerant distributor includes a bent portion at an intermediate position thereof in the horizontal direction, and wherein an outer diameter of the bent portion of the refrigerant distributor is less than an outer diameter of the bent portion of the first header , wherein the bent portion of the refrigerant distributor is formed by bending the inner pipe of the double-pipe structure. a heat exchange body including a plurality of flat tubes that extend in a vertical direction and are arranged in a horizontal direction with gaps therebetween, wherein a plurality of the heat exchange bodies are arranged in a direction of air flow to form a heat exchanger , and wherein a first header , into which hot gas refrigerant flows from a refrigerant circuit, is provided below one of the plurality of the heat exchange bodies that is at a most upwind position, characterised in that a refrigerant distributor having a double-pipe structure is provided below one of the plurality of the heat exchange bodies that is at a most downwind position, the double-pipe structure including an inner pipe having a plurality of refrigerant holes through which refrigerant flows and that are arranged with gaps therebetween, and an outer pipe into which the inner pipe is inserted, and wherein the heat exchanger has a refrigerant flow passage along which, when the heat exchanger functions as an evaporator, the refrigerant flows into the one of the plurality of the heat exchange bodies that is at the most downwind position through the refrigerant distributor and flows out of the one of the plurality of the heat exchange bodies that is at the most upwind position so that the refrigerant and air flow in opposite directions, wherein each of the first header and the refrigerant distributor includes a bent portion at an intermediate position thereof in the horizontal direction, and wherein an outer diameter of the bent portion of the refrigerant distributor is less than an outer diameter of the bent portion of the first header , wherein the bent portion of the refrigerant distributor is formed by bending the inner pipe of the double-pipe structure. <EOS>