To enhance a heat transfer efficiency by connecting a pair of parallel waveform plates at an interval to diffuse a liquid to be introduced between the plates by a capillary, thereby increasing a heat transfer area per liquid volume between the plates.

A liquid flowing part 3 has a pipe-like header 3a made of a similar material to a waveform plate 2, and a communicating part 3b for communicating the header 3a with a waveform heat transfer unit 1. A liquid 20 to be supplied to the header 3a is introduced into the unit 1 via the part 3b. A liquid flowing-out part also has a pipe-like header similar to the part 3, and a communicating part for communicating the header within the unit 1. The liquid flowing out from the unit 1 is introduced into the header via the communicating part, and discharged. Thus, a content stayed in the plate 2 is reduced, and a heat transfer area per liquid volume is increased.