PURPOSE: Titled resin composition which can provide decorative shets having good adhesion to substrates, prepared by mixing a specified unsaturated polyester with a specified diallyl phthalate prepolymer.

CONSTITUTION: An unsaturated polyester resin composition for coating basic inorganic decorative sheets, prepared by mixing (A) an unsaturated polyester obtained by reacting orthophthalic acid and/or isophthalic acid, fumaric acid and tricyclodecanedimethylol with (B) a prepolymer, MW 500W1,500, of diallyl phthalate, in amounts to provide a ratio, (A)/(B), of 100pts.wt./50W100pts.wt. The component (B) is a powder, MW 500W1,500, which is a di- to hexamer of monodiallyl phthalate, formed by the intermolecular reaction between terminal double bonds of diallyl phthalate of the formula.