In order to provide a fuel reservoir for a small-sized fuel cell which is suitably used as an electric power source for portable electronic appliances such as cellular phones, note type personal computers and PDA, assumed is a structure in which a fuel reservoir for a fuel cell detachably connected with a fuel cell main body is equipped with a fuel-storing vessel for storing a liquid fuel, a fuel discharge part and a follower which seals the liquid fuel and moves as the liquid fuel is consumed and into which a follower auxiliary member is inserted at a rear end of the liquid fuel, wherein the follower auxiliary member has no fluidity and is insoluble in the liquid fuel, and it has a cross-sectional area of 50% or more based on a cross-sectional area of the fuel-storing vessel in a diameter direction.