[Problem] Conventional copper pyrithione products are thought to elute too rapidly into seawater in tropical waters, and there is demand for the development of copper pyrithione having a larger average particle size to slow elution into seawater. Existing copper pyrithione products also tend to produce dust at the work site and have been shown to be injurious to health when inhaled into the lungs because they are acicular crystals. [Solution] The two above problems were simultaneously resolved by using an inorganic copper (II)/inorganic ammonium complex salt instead of an inorganic copper (II) salt, which is the conventional production raw material, and producing large particulate aggregates in which the average particle size of the resulting small copper pyrithione particles is 9-13 &mu；m.
