To prevent occurrence of white fuming by heating the atmosphere sucked from an upstream side of a cooling fan to a high temperature by a heater, and mixing it with the air which has cooled warm water to lower its humidity.

A distributing tube 3 is wound from an upper end to a lower end of a strut 2 while forming a gap 4 (ventilating part) for passing the atmosphere into a fan stack 1. A lower end vicinity of the strut 1 is smoothly bent radially outward of the stack 1, and a profile formed of the tube 3 is formed in a divergent cylindrical state. And, heating medium is supplied from a heating medium supply tube 5 connected to one end of the tube 3, heat exchanged with the atmosphere sucked by the medium, and exhausted or recovered from a heating medium exhaust tube 6 connected to the other end of the tube 3. When a cooling fan 54 is rotated, the atmosphere is passed through the gap while being heated by the tube 3, sucked into a cooling tower, mixed with the warm water cooling air which has cooled the warm water, and exhausted upward by the fan 54.