PROBLEM TO BE SOLVED: To provide a water-based mildew-proofing agent which exhibits persisting mildew-proofing effects and is excellently safe. SOLUTION: The water-based mildew-proofing agent comprises (a) 0.5-5.0 wt%, based on the whole amount, of a mildew-proofing component, (b) 0.2-5.0 wt% of a 14-18C monoalkyl-trimethylammonium salt as a water-repellent film-forming component, (c) 0-10 wt% of a lower alcohol, and (d) water. Preferably, the mildew-proofing component (a) is one or more selected from among benzalconium chloride, cetylpyridinium chloride, a didecyldimethylammonium salt and a monolauryltrimethylammonium salt. COPYRIGHT: (C)2006,JPO&NCIPI
