The present invention is an unsaturated polyester resin composition comprising an unsaturated polyester (a), a monomer (b) having one polymerizable carbon-carbon double bond, a monomer (c) having two or more of (meth)acrylate groups, a filler (d) having high thermal conductivity, a glass fiber (e), a low profile additive (f), a curing agent (g), and a polymerization inhibitor (h), wherein the ratio by weight of the ingredient (b) to the ingredient (c) is from 50:50 to 75:25 and the unsaturated polyester resin composition comprises 400 to 1400 parts by weight of the ingredient (d) based on the total 100 parts by weight of the ingredients (a), (b), and (c). This unsaturated polyester resin composition has excellent curing properties without losing storage stability which can be used to provide a cured product having a low mold shrinkage ratio and high thermal conductivity.