NOVELTY - The separator has a separator panel blocking gas, and an air electrode side collector inserted between the separator panel and a fuel electrode and an air electrode. The collector is configured to have a base collector material that is in contact with one of the electrodes, where the material is configured for collecting power. A rib is configured to be made of a linear piece that is in contact with the separator panel to form a gas flow route, where the height of the rib is smaller than an equivalent diameter of an opening in the material.    USE - Used in between adjacent fuel cell stacks (claimed) e.g. aqueous alkaline solution type fuel cell stack, phosphoric acid type fuel cell stack, molten carbonate type fuel cell stack, solid oxide type fuel cell stack, proton exchange membrane type fuel cell stack, direct methanol type fuel cell stack and solid polymer type fuel cell stack, for preventing reaction gas from permeating an membrane electrode assembly of a fuel cell system, where the fuel cell stacks together with an electricity storage device e.g. secondary battery and capacitor, are used as a power source for an accessory e.g. lighting unit, radio and power window, of a vehicle e.g. passenger car, bus, truck, passenger cart and freight cart.    ADVANTAGE - The rib is configured to be made of the linear piece that is in contact with the separator panel to form the gas flow route, and have the height that is smaller than the equivalent diameter of the opening in the base collector material, thus ensuring the supplying of sufficient amounts of gases to fuel cell electrodes with low power collection resistance, sufficient strength in the stacking direction, sufficient cooling of the electrodes and easy, low-cost manufacture.    DESCRIPTION OF DRAWING(S) - The drawing shows a block diagram of a structure of a fuel cell system.    Fuel supply line (21)    Hydrogen shut-off valve (24)    Fuel pressure adjustment valve (25)    Hydrogen supply valve (26)    Pressure sensor (27)    Outside air intake solenoid valve (35)    Air filter (37)    Fuel storage unit (73)    Water supply nozzle (76)    Air supply line (77)