To suppress the height of a crossflow cooling tower having white smoke preventing function.

A gas-liquid contact heat exchanging sections 5, 5 are disposed in the opposite sides of a tower body 3 and a pair of heaters 12, 12 are disposed in the air passage 9, i.e., the space between the sections 5, 5. The space between the heaters 12, 12 serves as an outer air introduction passage 14. On the side wall 7 of the tower body 3 where the gas-liquid contact heat exchanging section 5 is not disposed, an outer air introduction port 15 with damper 16 communicating with the outer air introduction passage 14 is provided. When there is a possibility of providing white smoke, outer air is introduced by opening the damper 16 and discharged to time air passage 9 after being heated through the heater 12. Heated air passed through the heater 12 and the heated and humidified air passed through the gas-liquid contact heat exchanging section 5 are mixed and stirred in the air passage 9 before being discharged from an exhaust port 10 to the atmosphere.