To provide a solid electrolyte for a fuel cell having high proton conductivity and water retaining property, excellent in mechanical and chemical stability.

The solid electrolyte for the fuel cell is made of porous silica 21 having fine pores 22 with uniform diameter, on inner wall of which perfluoroalkyl sulfonic acid groups are fixed. It is preferable that ordered array structure of the fine pores of the porous silica has a cubic array structure, the pore diameter of the fine pores of the porous silica ranges between 2 nm and 50 nm, and the porous silica is formed into grain shape or film shape.