Abstract: A new thermosetting resin composition is provided. The composition is characterized by the use of an epoxy group-containing polyester resin and a hardener having two or more carboxy groups. The epoxy group-containing polyester resin may be prepared by reacting an epoxy ester resin intermediate having both epoxy and alkyl ester groups (which, in turn, may be prepared by reacting a polyepoxy compound having at least two epoxy groups with a monoalkyl terephthalate) with a hydroxy group-containing polyester resin.The composition is particularly suitable for powder coatings. By using the thermosetting resin composition, powder coatings exhibit superior coated film properties, such as weatherdurability, corrosion resistance, mechanical properties and anti-blocking property. Further, as the composition contains no volatile constituents upon hardening when applied to powder coatings, no environmental pollution takes place.