In an inlet heat exchange unit, wherein a refrigerant's dryness is low and its flow distribution is likely to cause deviation, a number of heat exchange passages in an ascending flow path at an upstream side is less than the number of heat exchange passages in descending flow paths. Accordingly, refrigerant flowing in the ascending flow path increases, and a region in which the refrigerant lacks is reduced, thereby decreasing temperature variations. In an outlet heat exchange unit, wherein the refrigerant's dryness is high and its flow distribution is unlikely to cause deviation, the number of heat exchange passages a most downstream path is greater than the number of heat exchange passages in the immediately preceding path, thereby suppressing an increase in flow resistance in the most downstream path and keeping flow resistance in the outlet heat exchange unit low.