PURPOSE: To obtain a nondefective large molding easily under low-temperature and low-pressure conditions by applying vibrations to a resin composition comprising an unsaturated resin, fine inorganic filler particles, a specified fatty acid ester, etc., when it is compression-molded in a mold.

CONSTITUTION: A resin composition comprising 100 pts.wt. unsaturated polyester resin (A), 50-350 pts.wt. fine inorganic filler particles (B) and 0.1-10 pts.wt. at least one member (C) selected from among an aliphatic monohydric alcohol, a sorbitan fatty acid ester and a glycerol fatty acid ester each of which has a melting point of 40-100° is poured into a mold and compression-molded by heating under a pressure of 2-30kg/cm2 and the applied vibrations. Component C may be replaced by, for example, a neopentyl polyol fatty acid ester of a melting point of 40-120°C or a fatty acid amide of a melting point of 80-150°C. Examples of component C include stearyl alcohol, sorbitan palmitate and glycerol monolaurate. It is desirable that the vibrations have a frequency of 50-3000Hz and an amplitude of 5-30μm. Three-dimensional vibrations are desirable for a three-dimensional molding.