Patent ID: 8137863

Claim:
A fuel cell including a unit cell comprising: a membrane electrode assembly including a polymer electrolyte membrane with hydrogen ion conductivity, and an anode and a cathode sandwiching said polymer electrolyte membrane; an anode-side separator with electric conductivity including a fuel gas flow channel for supplying and discharging a fuel gas to and from said anode; a cathode-side separator with electric conductivity including an oxidant gas flow channel for supplying and discharging an oxidant gas to and from said cathode; and an anode-side gasket disposed on a circumference portion of said membrane electrode assembly in a face of said anode-side separator and a cathode-side gasket disposed on a circumference portion of said membrane electrode assembly in a face of said cathode-side separator, for sealing said fuel gas and said oxidant gas, respectively, wherein an anode-side gap of a substantially rectangular shape is formed between said anode-side gasket and said membrane electrode assembly in the side of said anode and a cathode-side gap of a substantially rectangular shape is formed between said cathode-side gasket and said membrane electrode assembly in the side of said cathode, and at least one of said anode-side gasket and said cathode-side gasket has: an annular main body portion disposed along the circumference portion of said membrane electrode assembly; and an extra sealing portion being integrated with said main body portion and bridging two points on opposite sides of said main body portion such that, among two pairs of gap portions opposing to each other in said anode-side gap and said cathode-side gap, said extra sealing portion partially intersects with one pair of said gap portions having a larger pressure gradient of said fuel gas and said oxidant gas in a direction from an upstream side to a downstream side of said fuel gas flow channel and said oxidant gas flow channel.