A fuel cell is constructed in such a manner that a porous film which is electrolyte-resistant and inactive to fuel is allowed to adhere to one surface of a fuel electrode and an electrolyte containing hydrazine fuel supplied to the cell and passing through said porous film and fuel electrode reaches the side of an oxidation electrode. In such fuel cell, self-decomposition of fuel due to direct contact with the fuel electrode occurs in a small degree and utilization efficiency of fuel is high. Furthermore, such fuel cell can be operated with an electrolyte containing fuel in a high concentration.