NOVELTY - Driving a fuel cell system (100) involves sequentially supplying a humidified fuel and an oxidizer to a fuel cell stack (50); measuring the temperature of each of unit cells in the fuel cell stack; detecting a unit cell having the lowest temperature among the measured temperature of each of the unit cells; and decreasing humidification temperature of the fuel to be lower than the lowest temperature.    USE - For driving a fuel cell system (claimed) e.g. polymer electrolyte membrane fuel cell, used as a power source for a variety of applications such as for a pollution-free vehicle, home power equipment, mobile communication equipment, military equipment, medical equipment.    ADVANTAGE - The humidification temperature of the humidifying unit is higher than the temperature of the unit cell having the lowest temperature during a predetermined time period in the initial driving stage. Thus, the water supplied during the predetermined time period is absorbed by the membrane electrode assembly of the corresponding unit cell so that water condensation does not occur. Thus, blocking of the fuel path due to condensation of the humidified fuel in the fuel cell stack can be prevented.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for fuel cell system comprising a fuel cell stack including a membrane electrode assembly (MEA) (52b) and unit cells, where the MEA having a membrane, cathode disposed at a first side of the membrane and an anode disposed at a second side of the membrane, each unit cell of the unit cells has a separator attached to the MEA; fuel supply unit configured to supply a fuel to the fuel cell stack; an oxidizer supply unit (30) configured to supply an oxidizer to the fuel cell stack; humidifying unit (20) configured to provide humidity to the fuel; and controller (70) configured to detect a unit cell among the unit cells having the lowest measured temperature and configured to control a humidification temperature.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of fuel cell system.    Fuel supply unit (10)    Humidifying unit (20)    Oxidizer supply unit (30)    Membrane (52b)    Controller electrode assembly (70)    Fuel cell system (100)