To provide a deodorization method of exhaust gas of a circulation water cooling tower, capable of suppressing generation of an odor from the circulation water cooling tower.

The circulation water cooling tower includes: a circulation water inlet for introducing circulation water; a sprinkler device for sprinkling the circulation water introduced from the circulation water inlet toward a downstream side; a gas-liquid contact part provided on a downstream side of the sprinkler device, at a position through which air sucked from an air suction part passes; and a water supply tank provided on a downstream side of the gas-liquid contact part, for receiving and storing the sprinkled circulation water. The air suction part sucks cooling air from a side part of the circulation water cooling tower into the inside of the circulation water cooling tower. The circulation water cooling tower also includes a cooling tower fan provided at an upper part of the circulation water cooling tower, for exhausting the air sucked from the air suction part to the outside of the circulation water cooling tower, through the gas-liquid contact part. In the deodorization method of exhaust gas of the circulation water cooling tower, ozone in a gaseous state is introduced from an upstream side of the gas-liquid contact part into the inside of the circulation water cooling tower.