To provide a method for producing an antimicrobial additive in which the antimicrobial additive can be added and mixed into a water-based paint by improving the dispersibility of the antimicrobial additive which is an antimicrobial powder.SOLUTION: Provided is a method for producing an antimicrobial additive added for imparting antimicrobial property to water-based paint, comprising a step in which an antimicrobial powder containing each component of (1) silver oxide, (2) zirconium phosphate, (3) zinc oxide, (4) N',N-dimethylamino-N'-phenyl-N'-(fluorodichloro-methylthio)sulfone, (5) 2- methoxycarbonyl-amino-benzimidazole, (6) debuconazole, (7) N- (fluorodichloro-methylthio)-phthalimide and (8) 2-propenoic acid homopolymer sodium salt, and an ion-exchanged water are stirred by a self-revolution type stirrer.SELECTED DRAWING: Figure 1【課題】抗菌パウダーである抗菌添加剤の分散安定性を良くして水性塗料へ添加・混入できるようにする。【解決手段】水性塗料に抗菌性を持たせるために添加する抗菌添加剤の製造方法であって、（１）酸化銀、（２）リン酸ジルコニウム、（３）酸化亜鉛、（４）Ｎ'，Ｎ－ジメチルアミノ－Ｎ'－フェニル-Ｎ'－(フルオロジクロロメチルチオ)スルホン、（５）２－メトキシカルボニルアミノ－ベンゾイミダゾール、（６）デブコナゾール、（７）Ｎ－（フロロジクロロメチルチオ）－フタルイミド、（８）２－プロペン酸ホモポリマーナトリウム塩の各成分を含有する抗菌パウダーとイオン交換水とを自公転式撹拌機によって撹拌する。【選択図】図１
