An evaporator comprises front and rear header portions, and U-shaped flat tubular portions arranged in parallel and each connected at opposite ends thereof to the header portions. Each of the header portions is provided with a partition for blocking a refrigerant flowing inside thereof and directing the refrigerant toward some of the flat tubular portions to thereby form a refrigerant channel comprising a plurality of paths each turned by the partition. The rear header portion of the final path is provided with a refrigerant dividing wall having refrigerant apertures for passing therethrough a portion of the refrigerant flowing in from the path immediately upstream from the final path, with the remaining portion of the refrigerant blocked by the wall and directed toward some of the flat tubular portions.