To provide a cooling tower capable of preventing splashing water from a filler from being discharged to the outside of the cooling tower through an outside air suction port when the operation of a blower is stopped.

This cooling tower 1 is provided with a louver 15 attached to the outside air suction port 3, the filler 6 through which circulating water W flows down, and the blower 7 to cool the circulating water W flowing down through the filler 6 by outside air Q sucked through the outside air suction port 3 by operating the blower 7. The louver 15 is composed of a plurality of louver blades 16 arranged vertically at many steps and louver blade supports 17 supporting these louver blades 16. The upper end side of each louver blade 16 is pivotally fixed to the louver blade support 17, and each louver blade 16 can swing freely between an opening position where an air passage 30 is formed between the louver blade 16 and the adjacent louver blade 16 and a closing position where the outside air suction port 3 is blocked.