Resin composition for thermosetting coating

A resin composition for thermosetting coating, which comprises (a1) an acrylic copolymer having a particular acid value and/or (a2) an acrylic copolymer having a particular acid value and a particular hydroxyl value, (b) an acrylic copolymer having a particular epoxy equivalent, (c) a monobasic acid having a dissociation constant (pKa) of 3 or less, and, as necessary, (d) an amino resin and (e) a quaternary phosphonium salt, and wherein the equivalent ratio of the acid group of (a1) and/or (a2) and the epoxy group of (b) is 1:0.5 to 0.5:1 and the amounts of (c), (d) and (e) are 0.01-5 parts by weight, 1-25 parts by weight and 0.01-3 parts by weight, respectively, per 100 parts by weight of the total of (a1) and/or (a2) and (b). Said resin composition, when used as a clear coating for automobiles, is superior in film appearance, acid resistance, solvent resistance, water resistance, weatherability, storage stability and low temperature curing.