A resin composition for water paint, wherein the resin composition includes water and a vinyl-modified epoxy ester resin (A) which includes a fatty acid chain to which a vinyl polymer portion is combined, and the vinyl polymer portion comprises a structure which includes a carboxyl group at the terminal end represented by the general formula (I), and part of or all of the structure represented by general formula (I) is neutralized with a basic compound. (in the formula, n represents a number of 1 to 10, and R.sup.1 represents an alkylene group having 2 to 18 carbon atoms)