The present invention discloses a thermosetting aqueous paint, comprising an oligomer (A-1), having a specific acid value, hydroxyl value and number average molecular weight, and obtained by reacting a compound having at least one hydroxyl group and at least one carboxyl group in a molecule thereof, a monoepoxide compound having a long-chain hydrocarbon group, and as necessary, a polyvalent carboxylic acid and/or polyvalent carboxylic acid anhydride, and/or a polyester resin (A-2) obtained by further reacting a polyvalent carboxylic acid and/or a polyvalent carboxylic acid anhydride and/or a polyisocyanate compound with the oligomer, and a crosslinking agent (B); and also discloses a method for forming a paint film using this paint.