An air-conditioning apparatus comprising: - a heat exchanger including a plurality of heat transfer tubes in which refrigerant flows, the plurality of heat transfer tubes being arranged so as to be spaced apart from each other in a vertical direction, and a header manifold that has a flow space defined inside the header manifold and extending in the vertical direction, the header manifold allowing refrigerant to flow into the plurality of heat transfer tubes from a plurality of branch tubes, the plurality of branch tubes being arranged so as to be spaced apart from each other in the vertical direction; - an axial fan including a blade disposed around a boss that rotates, the blade having a rotational plane that faces the plurality of heat transfer tubes in a horizontal direction; and - a refrigerant circuit to direct the refrigerant into the flow space such that the refrigerant flows upward in a two-phase gas-liquid state, and to cause the refrigerant to evaporate in the heat exchanger, wherein the refrigerant flows in the header manifold in an annular or churn flow pattern in which gas-phase refrigerant collects at a center of the header manifold and liquid-phase refrigerant collects on a wall surface of the header manifold, and wherein, when a distance from a center of the flow space in a horizontal plane is represented on a scale of 0 to 100%, where 0% is the center of the flow space and 100% is a position of the wall surface of the header manifold, among the plurality of branch tubes located within a height range that allows the blade to rotate, a majority of the branch tubes located at or below a height of the boss are inserted into the header manifold such that distal ends of the branch tubes are positioned at 0 to 50% of the distance from the center, and a majority of the branch tubes located above the height of the boss are connected to the header manifold such that distal ends of the branch tubes are positioned at more than 50% of the distance from the center. - a heat exchanger including a plurality of heat transfer tubes in which refrigerant flows, the plurality of heat transfer tubes being arranged so as to be spaced apart from each other in a vertical direction, and a header manifold that has a flow space defined inside the header manifold and extending in the vertical direction, the header manifold allowing refrigerant to flow into the plurality of heat transfer tubes from a plurality of branch tubes, the plurality of branch tubes being arranged so as to be spaced apart from each other in the vertical direction; a plurality of heat transfer tubes in which refrigerant flows, the plurality of heat transfer tubes being arranged so as to be spaced apart from each other in a vertical direction, and a header manifold that has a flow space defined inside the header manifold and extending in the vertical direction, the header manifold allowing refrigerant to flow into the plurality of heat transfer tubes from a plurality of branch tubes, the plurality of branch tubes being arranged so as to be spaced apart from each other in the vertical direction; - an axial fan including a blade disposed around a boss that rotates, the blade having a rotational plane that faces the plurality of heat transfer tubes in a horizontal direction; and - a refrigerant circuit to direct the refrigerant into the flow space such that the refrigerant flows upward in a two-phase gas-liquid state, and to cause the refrigerant to evaporate in the heat exchanger, wherein the refrigerant flows in the header manifold in an annular or churn flow pattern in which gas-phase refrigerant collects at a center of the header manifold and liquid-phase refrigerant collects on a wall surface of the header manifold, and wherein, when a distance from a center of the flow space in a horizontal plane is represented on a scale of 0 to 100%, where 0% is the center of the flow space and 100% is a position of the wall surface of the header manifold, among the plurality of branch tubes located within a height range that allows the blade to rotate, a majority of the branch tubes located at or below a height of the boss are inserted into the header manifold such that distal ends of the branch tubes are positioned at 0 to 50% of the distance from the center, and a majority of the branch tubes located above the height of the boss are connected to the header manifold such that distal ends of the branch tubes are positioned at more than 50% of the distance from the center. wherein the refrigerant flows in the header manifold in an annular or churn flow pattern in which gas-phase refrigerant collects at a center of the header manifold and liquid-phase refrigerant collects on a wall surface of the header manifold, and wherein, when a distance from a center of the flow space in a horizontal plane is represented on a scale of 0 to 100%, where 0% is the center of the flow space and 100% is a position of the wall surface of the header manifold, among the plurality of branch tubes located within a height range that allows the blade to rotate, a majority of the branch tubes located at or below a height of the boss are inserted into the header manifold such that distal ends of the branch tubes are positioned at 0 to 50% of the distance from the center, and a majority of the branch tubes located above the height of the boss are connected to the header manifold such that distal ends of the branch tubes are positioned at more than 50% of the distance from the center.