A resin composition containing fine paper powder used in molding is obtained by using a non-intermeshing type counter-rotating twin-screw kneading extruder (10) having rotor units (11b, 12b) disposed in at least a part of screws (11, 12), respectively, to knead a raw material containing a fine paper powder of an average particle diameter of 10 to 100 μm from 20 to 70 parts by weight, and a thermoplastic resin from 30 to 80 parts by weight, with a sum of the fine paper powder and the thermoplastic resin being 100 parts by weight, at a temperature of no more than 210° C.