The present invention provides a plant resin composition containing a polylactic acid, a thermoplastic resin, and a compatibilizer, in which the compatibilizer is a polymeric material formed from an alkyl methacrylate monomer and has a weight-average molecular weight of not less than 950,000 and not more than 4,100,000. The alkyl methacrylate monomer preferably is at least one selected from methyl methacrylate, ethyl methacrylate, propyl methacrylate, and butyl methacrylate. By forming a plant resin molded product with this plant resin composition, the impact resistance and the heat resistance of the plant resin molded product can be enhanced.