PURPOSE: To low-odor unsaturated polyester resin composition, prepared by using a dimethyl ester of a dimerized methacrylic acid as a crosslinking monomer component.

CONSTITUTION: An unsaturated polyester resin body (e.g., "Yupika 8542", a product of Nippon Yupika Co., Ltd.) is mixed with a dimethyl ester of dimerized methacrylic acid of the formula, and about 0.5W10wt%, based on the resin composition, curing agent, preferably, an organic peroxide whose 10hr half-life decomposition temperature is above 90°C, e.g., t-butyl perbenzoate.