A heat exchange tube having a flat shape includes a plurality of fluid paths having a circular cross section and extending in a longitudinal direction of the tube. Each fluid path is parallel to each other fluid path. The tube is dimensioned such that a distance between two adjacent fluid paths is defined as Wt, and a circumferential thickness between a surface of the tube and an outermost fluid path is defined as Ht. The distance Wt and the circumferential thickness Ht have a relationship as 0.42≦Ht/Wt≦0.98.