PURPOSE:To prepare the title compsn. having excellent impact resistance, heat resistance, etc., by melt-blending polyphenylene ether and a specified diene block polymer, adding therein an aliph. polyamide and melt-blending them. CONSTITUTION:Polyphenylene ether (a) and one or more diene block copolymers (b) selected from an A-B-A' type block copolymer elastic substance (wherein A and A' are the same or different copolymerized arom. hydrocarbon blocks; B is a polymerized conjugated diene block) and a hydrogenated A-B-A' type block copolymer elastic substance wherein the intermediate blocked part B is hydrogenated are fed in a feeding hole 3 of the driving side of an intermeshing, equidirectional biaxial extruder and melt-blended. Thereafter, an aliph. polyamide 6 whose melt viscosity at 280-380 deg.C is lower than that of the component (a) is fed and melt-blended.