PURPOSE: An antifouling coating composition that contains a hard-soluble copper compound and a reductive compound that has a lower oxidation-reduction potential than the copper compound and is hard soluble in water, thus preventing and protecting ships and underwater constructions from being fouled by water life.

CONSTITUTION: (A) A hard-soluble copper compound, which is preferably of solubility of less than 1×10-4mole/l in sea water at 8.2pH and 20°C and (B) a reductive substance that has a lower oxidation-reduction potential than the component A and is hard soluble in water, preferably at least one selected from tin, antimony, zinc, chromium, iron, nickel, lead and titanium are contained to give the objective coating composition.

EFFECT: The resultant composition permits rosin to be removed, resulting in increase of the strength of antifouling coating films.