Disclosed is a fuel cell comprising a fuel cell body (stacked body) including a unit cell having an electromotive section in which an electrolyte membrane is sandwiched between a fuel electrode and an oxidant electrode, and a liquid fuel tank for storing a liquid fuel that is to be supplied to the fuel cell body and connected to the fuel cell body. The liquid fuel is introduced by the capillary action into the unit cell included in the fuel cell body and vaporized within the unit cell so as to be supplied to the fuel electrode, thereby generating an electric power. The liquid fuel tank is provided with a pressure adjusting mechanism for introducing a required amount of the liquid fuel from a liquid outlet port into the unit cell.