NOVELTY - A fuel-cell system (100) consists of a fuel cell unit (2), a condensed-water tank (7), a water feed route (9), and a water purification apparatus (14). The water purification apparatus consists of an ion-exchange resin layer (15), an antibacterial agent layer (17) arranged in the upstream of the flow direction of ion-exchange resin layer, an activated-carbon layer (16) arranged between the ion-exchange resin layer and antibacterial agent layer, and clearance gap (I) formed between the activated-carbon layer and ion-exchange resin layer.    USE - Fuel cell system is used in fuel battery cogeneration systems.    ADVANTAGE - The fuel cell system suppresses proliferation of microorganisms in the water route during shutdown, without using components e.g. electric heater, and can be operated without prolonged maintenance. Flowing of antibacterial agent out of the water purification apparatus when operation of fuel cell system is restarted is suppressed or prevented when the antibacterial agent is eluted and retained in the water purification apparatus. The influence of antibacterial agent with respect to downstream hydrogen supply unit or fuel cell is reduced or prevented.    DETAILED DESCRIPTION - A fuel-cell system consists of a fuel cell unit which produces electric power using fuel gas (GG) and oxidizing agent gas, and supplies electric power, a condensed-water tank which stores the condensed water collected from the gas discharged from the fuel cell unit, a water feed route which supplies water to the fuel cell unit from the condensed-water tank, and a water purification apparatus arranged on the water feed route for purifying ions in water. The water purification apparatus consists of an ion-exchange resin layer, an antibacterial agent layer arranged in the upstream of the flow direction of ion-exchange resin layer, an activated-carbon layer arranged between the ion-exchange resin layer and antibacterial agent layer, and clearance gap (I) formed between the activated-carbon layer and ion-exchange resin layer.    DESCRIPTION OF DRAWING(S) - The drawing shows a block diagram of the fuel cell system. (Drawing includes non-English language text)    Fuel cell unit (2)    Condensed-water tank (7)    Water feed route (9)    Water purification apparatus (14)    Ion-exchange resin layer (15)    Activated-carbon layer (16)    Antibacterial agent layer (17)    Fuel cell system (100)    Fuel gas (GG)