To provide a proton conductive material resistant to the elution of an acid component from the proton conductive material to a water-containing solution and free from the lowering of the ion conductive property.

The proton conductive material has an acid residue bonded to a main chain with covalent bond through a linking group and is crosslinked with two or more kinds of crosslinking groups. Particularly, the proton-conductive material has a main chain composed of carbon-carbon bond and contains a mesogen, a crosslinked structure having an Si-O bond and a crosslinked structure having a C-O bond or a C-C bond. The invention further provides a membrane and electrode assembly of the proton conductive material and its use in a fuel cell.