A process for producing a polyphenylene ether resin composition comprising (A) a polyphenylene ether and (B) styrene resins including a rubber-modified polystyrene containing polybutadiene having a cis-1,4 bond content of 90% or higher, which comprises a first step in which the polyphenylene ether (A) is melt-kneaded together with part or all of the styrene resins excluding (B1) a rubber-modifiedpolystyrene containing unhydrogenated polybutadiene and a second step in which the remainder of the styrene resins, which includes (B2) a rubber-modified polystyrene containing polybutadiene having acis-1,4 bond content of 90% or higher, is melt-kneaded therewith; and a polyphenylene ether resin composition obtained by the process. By the process, a modified PPE can be stably supplied which is free from various appearance defects including black spots, particles which have not undergone melting, and unevenness of color and is excellent in practical properties including thermal stability in residence, resistance to exposure to heat, and low-temperature impact resistance, in particular, resistance to thermal deterioration.