PURPOSE: To provide a composition comprising an unsaturated polyester, a mixture of styrene and a specific di-ester, and a natural fiber, which gives the molded bodys having a low residual monomer content and no styrene odor by heat press molding.

CONSTITUTION: The object composition comprises a mixture of 1-85 wt.% of (A) an unsaturated polyester, and 15 to 99 wt.% of (B) a mixture of (i) styrene and (ii) ester of 2-9C (cyclic)aliphatic diol and di-(meth)acrylic acid [respectively, based on the weight of the said mixture of (A) and (B)], (C) a natural fiber (suitably a jute fiber mat) and (D) ordinary additives. 1,4-Butane-diol- dimethacrylate is preferable as the ingredient (ii) and, for example, a polymerization initiator, a filler or the like can be used as the ingredient (D). It is preferable to obtain the said composition by allowing the component (A) to be dissolved in the component (B) and allowing the component (C) to be impregnated with the said resin solution.