NOVELTY - A fuel cell (10S) comprises power generation layer unit, water absorbing layer (11), and oxygen supply layer (2). The power generation layer unit moves hydrogen ion from first surface to second surface and causes the hydrogen ions to react with oxygen on second surface. The oxygen supply layer diffuses oxygen in atmosphere from a side surface of supply the oxygen to the second surface. The water absorbing layer has stability of holding liquid water higher than the oxygen supply layer.    USE - The fuel cell is useful for making fuel cell system used for portable electronic equipment, e.g. digital camera, digital video camera, small projector, small printer, and notebook personal computer.    ADVANTAGE - The fuel cell has high dischargeability, is capable of stably maintaining high generation efficiency, and realizes high output even in small size and light weight. The fuel cell is capable of removing unnecessary liquid water form power generation layer. The fuel cell provides system that requires no supply of power from outside for activation because a circulation mechanism and blower of the atmosphere increases parts count that contradicts the miniaturization and reduction in weight of fuel cell system. The fuel cell is capable of discharging generated water generated in accordance with power generation from oxygen supply layer easily without depending upon a forceful and active procedure, maintaining high power generation efficiency stably even at high current value, and realizing high output even with a small size and light weight.    DETAILED DESCRIPTION - The water absorbing layer is communicated with oxygen supply layer and is placed opposed to the power generation layer unit with oxygen supply layer(s) interposed between them. The water absorbing layer is sheet shaped unit made of material different from the oxygen supply layer. The material for the water absorbing layer has hydrophilicity greater than the material for oxygen supply layer. The air permeability of oxygen supply layer in direction communicating the power generation layer unit with water absorbing layer greater than the direction along a surface of the power generation layer unit. The fuel cell includes diffusion layer (3), and number of through holes communicating the oxygen supply layer with power generation unit in the diffusion layer. The water absorbing layer is opened to the atmosphere outside the oxygen supply layer. The diffusion layer is between supply oxygen and power generation layer unit with average opening size of tissue smaller than the oxygen supply layer and larger than the power generation layer unit. The supply of oxygen from the side surface from which oxygen taken into the power generation layer unit depends upon natural diffusion of oxygen through the oxygen supply layer. The fuel cell can also comprises electrolyte film, catalyst layer, two diffusion layers, fuel supply layer (6), oxygen supply layer, water absorbing layer, and collector (1). The fuel cell has opening in part of the side surface parallel to the proton conduction direction of the electrolyte film among side surfaces of the fuel cell. The water absorbing layer is between the oxygen supply layer and collector. An end portion of the water absorbing layer is present on one of the plane including the opening and an opposite side of the fuel cell with plane including the opening being a reference. The water absorbing layer includes regions with hydrophilicity different from that of the different region. The water absorbing layer is not contact with the diffusion layer. An INDEPENDENT CLAIM is included for fuel cell system.    DESCRIPTION OF DRAWING(S) - The figure shows cross sectional view of the fuel cell cut along a plane parallel to plane including openings.    Collector (1)    Oxygen supply layer (2)    Diffusion layer (3)    Membrane electrode assembly (4)    Fuel supply layer (6)    Separator (7,9)    Fuel cell (10S)    Water absorbing layer (11)