PURPOSE: To increase strength and phosphoric acid holding capacity as well by performing hydrophilic treatment to fluorine contained fibers which are woven into cloths.

CONSTITUTION: When fluorine contained fibers which are high in strength by themselves are woven into cloths, the cloths are furthermore strengthened as a whole because the fibers are lined up in the surface firection, and this thereby increase the tension strength of a matrix to a great extent. Since the internal resistance of a fuel battery is increased in proportion to the thickness of the matrix, if it is made thinner, internal resistance can be reduced by that much. Affinity with phosphoric acid is imparted to the fluorine contained fibers by means of hydrophilic treatment, which thereby allows strength to be increased while phosphoric acid holding capacity is sufficiently secured. When the matrix as mentioned above is used, internal resistance is thereby reduced while the moving speed of phosphoric acid can also be increased.