To increase an evaporating efficiency of an evaporator.

Refrigerant water is dispersed from a water receptor pan 44 at the upper part of an evaporating pipe 41a and is expanded at an evaporating pipe 41a having a groove 63 producing an oxidization film 62 and flows down and at the same time a part of the refrigerant water is flowed down from between the evaporating pipe 41a and a coil 60 while it is being guided by the coil 60 in a helical manner. At that time, the refrigerant water flows like a convection stream and is contacted with all the regions in the evaporating pipe 41a to evaporate, so that its evaporating efficiency is improved.