The invention provides a proton conductive membrane which, even when reduced in thickness, does not allow penetration of an electrode to prevent a short circuit between electrodes and which permits sufficient generating performance. A proton conductive composition capable of forming the membrane is also provided. The proton conductive composition includes a nonconductive filler and a polyarylene having a sulfonic group. The proton conductive membrane, comprising the composition, contains the nonconductive filler in an amount of 3 to 50% by volume, and the nonconductive filler particles have diameters ranging from 3 to 90% the thickness of the membrane.