A polymer electrolyte fuel cell comprising: a hydrogen ion-conductive polymer electrolyte membrane; an anode and a cathode with the electrolyte membrane interposed therebetween; an anode-side conductive separator having a gas flow channel for supply of a fuel gas to the anode; and a cathode-side conductive separator having a gas flow channel for supply of an oxidant gas to the cathode, wherein each of the anode and the cathode comprises at least a catalyst layer in contact with the electrolyte membrane and a gas diffusion layer in contact with the catalyst layer and the separator, and at least one of the anode and the cathode contains a compound represented by the formula (I): R.sub.1--O--{(C.sub.2H.sub.4O).sub.n--(C.sub.3H.sub.6O).sub.m}--R.sub.2 (I) where R.sub.1 and R.sub.2 are independent of each other and each represents a hydrogen atom or an alkyl group having not less than 5 and not more than 15 carbon atoms, n and m are integers which satisfy 0.ltoreq.n.ltoreq.5, 0.ltoreq.m.ltoreq.5 and 1.ltoreq.n+m.ltoreq.5, and when neither n nor m is 0, at least one of the ethylene oxide group and at least one of the propylene oxide group are arranged in a random fashion.