Provided is a modified polyphenylene ether resin which is a reaction product of 100 parts by weight of (A) a polyphenylene ether having a main chain structure of the following formula (1): (wherein R1 and R4 each independently represents hydrogen, a primary or secondary lower alkyl, a phenyl, an aminoalkyl or a hydrocarbonoxy, and R2 and R3 each independently represent, hydrogen, a primary or secondary lower alkyl or a phenyl), and 0.01 to 10.0 parts by weight of (B) a modifier selected from conjugated non-aromatic diene compounds, dienophilic compounds having one dienophile group and precursors of the diene or dienophilic compounds, wherein the number of rearrangement structures each represented by the following formula (2): (wherein R1, R2, R3, and R1 have the same meanings as defined above in the formula (1)) is less than 0.01 per 100 phenylene ether units of the formula (1). The resin has sufficient functionality and is well balanced between color tone/appearance and heat resistance/mechanical physical properties.