An evaporator 1 is configured such that two heat exchange tube groups 16, each composed of a plurality of heat exchange tubes 15, are provided between a pair of header tanks 2, 3, while being separated from each other in a front-rear direction. Each of the header tanks 2, 3 includes two header sections 5, 6, 11, 12. Each header tank 2, 3 includes a first member 21, 93 to which the heat exchange tubes 15 are connected, and a second member 22, 94 which is joined to the first member 21, 93 and covers the side of the first member 21, 93 opposite the heat exchange tubes 15. Partition portions 41, 42 for dividing the interiors of the header section 5, 6, 11, 12 into upper and lower spaces 5a, 5b, 6a, 6b are provided on the second member 22, 94 of the header tank 2, 3. Through holes 47, 51A, 101, 102 for establishing communication between the upper and lower spaces 5a, 5b, 6a, 6b of the header section 5, 6, 11, 12 are formed in the partition portions 41, 42. The second member 22, 94 is formed by bending a metal plate. This evaporator 1 requires a reduced number of components and facilitates production work.