An unsaturated polyester resin composition for use in pressure molding, which comprises an unsaturated polyester resin and fillers consisting essentially of (a) calcium carbonate powder which passes a 325 mesh sieve, (b) an inorganic mineral particulate which passes a 12 mesh sieve and is retained on a 200 mesh sieve and (c) glass fibers having a length larger than 0.2 mm, wherein the ratio by weight of (a) to (b) is within a range of from 0.3 to 10, the ratio of (a)+(b) to the unsaturated polyester resin is within a range of from 1.5 to 7, and the ratio of (c) to the total weight of the resin, calcium carbonate, silica sand and glass fiber is within a range of from 0.01 to 0.25.