PURPOSE: To provide a sealing method ensuring freedom from damages to a polymeric electrolyte film, and ensuring safety by densifying the peripheral section of an electrode for a solid polymeric fuel cell and applying a gas seal to the densified section.

CONSTITUTION: The peripheral sections of electrodes 18 and 18 for a solid polymeric fuel cell are densified, and the densified sections 20 and 20 are used for gas sealing with a packing 21, in conjunction with frames 10 and 11, and separators 16 and 17. This densifying method is not limited in particular. An example of the method, however, is that the peripheral sections of the electrodes 18 and 18 are impregnated with a solution of a densifying agent formed out of an adhesive or the like, and a solvent is removed from the solution whenever necessary. Also, the densifying agent to be used is preferably a polytetrafluoroethylene resin dispersed agent. This densifying agent is in particular effective for the gas diffusion electrode where a catalyst layer made of catalyst particulates, an electrolyte and polytetrafluoroethylene is on water repellent carbon paper.