To provide simple a deodorizing technology which is excellent in deodorizing effect against the smell of excretion from a sewage tank of a tank type toilet.

The liquid deodorant having a pH of 1.0-6.0 is applied to the sewage tank of the tank type toilet, which contains: (1) polyphenol; (2) organic acid; and (3) a solvent which is made of a compound containing a hydroxyl group or the compound containing a hydroxyl group and water, and dissolves the polyphenol and the organic acid. The liquid deodorant hardly freezes even in a cold region when using an antifreeze liquid containing the liquid deodorant as cleaning water, so that the tank type toilet is usable. A more excellent effect is obtained when mixing perfume of 0.1-10 mass% and the liquid deodorant.