Abstract: A curable unsaturated polyester resin composition contains graft copolymers each having 10-60 weight % of a first constituent given by ##STR1## 38-89.7 weight % of a second constituent given by ##STR2## and 0.3-2 weight % of a third constituent which is a vinyl monomer unit having carboxylic acid or carboxylic anhydride groups, unsaturated polyester, vinyl monomer, a filler, a curing catalyst, and reinforcing fibers, where either of R.sup.1 and R.sup.2 is H, the other being either H or CH.sub.3, R.sub.3 is ethylene group or propylene group, R.sup.4 is hydrocarbon group with 1-18 carbton atoms, R.sup.5 is alkyl group with 1-4 carbon atoms, R.sup.6 is alkyl group with 1-3 carbon atoms, m is 6-90 and n is 1-5.