TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - The separator is particularly provided with a cooling means. Between the separators, there is a sealant in the electrode peripheries or the gaps of the electrode peripheries. The whole of the side of the laminate cell has a sealant. A manifold for supplying fuel gas or oxidizing gas to the electrodes is installed at the side of such laminate cell. A heat exchanger is available for the cooling water discharged from the polymer electrolyte fuel cell and fuel gases supplied to it, and humidifying and heating are operated simultaneously with a humidifier.    TECHNOLOGY FOCUS - POLYMERS - The sealant is a polymeric compound of formula (I).R1-(-Xi-(CH2-C(CH3)2)m-Yi-)i-R2 (I)R1, R2 = non-functional group-containing terminalXi, Yi = independently polymerizable functional group which is the crosslinking point after polymerizationm = integer not less than 1 showing the repeating units of isobutylene oxide oligomeri = not less than 1 showing polymerization degree.The separator is a carbonaceous material, metallic material or a polymer of formula (I). The polymerization degree of the polymer is not less than 8000. At least a part of the sealant is from a number of layers. Such sealant is preferably in a 3-layered structure formed from a pair of elastic resin layers sandwiching a heat-resistant hard resin layer. This hard resin layer is particularly a polyethylene phthalate resin, while the elastic resin layer is made from a polymer of formula (I). Preferred Definitions: Xi, Yi = independently allyl, (meth)acryloyl, isocyanate or epoxy; and the repeating units, m, of the isobutylene oxide oligomer is particularly 56-72.    EXAMPLE - Platinum was immobilized onto carbon powder in 1:1 ratio and then applied as a slurry of catalyst layer to both sides of a carbon paper (previously treated with fluoro resin) as electrode together with the application of a solid polymer electrolyte film between the electrodes (as shown in Figure). Then a unit cell was fabricated with installation of separators and sealed with other unit cells to form a polymer electrolyte fuel cell as specified.