PURPOSE: The title coating material capable of giving films having improved antifouling properties, prepared by mixing two liquids, obtained through incorporation of a triphenyltin compound and a copper compound as antifouling agents into a solution of a synthetic resin free from carboxyl groups in an organic solvent under specific conditions, before coating.

CONSTITUTION: A two-pack antifouling coating material of the organic solvent type is prepared as follows: (a) A synthetic resin or rubber, e.g. chlorinated rubber or acrylic resin, free from carboxyl groups or its mixture with a plasticizer is incorporated with (b) at least one type of (b1) a triphenyltin compound, e.g. triphenyltin acetate, or (b2) a copper compound, e.g. cuprous oxide, as antifouling agents separately to give liquids (A) and (B). The liquids (A) and (B) are mixed immediately before use. The amounts of (b1) and (b2) are 5W25wt% and 20W50wt% respecively in mixing the liquids.