PURPOSE: To provide a while smoke preventing device, capable of effecting easily a white smoke preventing countermeasure in winter without deteriorating the cooling capacity of the tower in summer and capable of applicating the device easily to any cooling tower installed already.

CONSTITUTION: A white smoke preventing device is provided with shade members 23, equipped with a water conducting port and installed across the upper parts of neighboring filler members 21, 21, baloon type water shielding members 24, expanded by pouring fluid through the water conducting ports 23c to blockade the water conducting port 23c, and fluid introducing means 25, pouring or discharging the fluid into or out of the water shielding members 24.