A fuel for a fuel cell system comprising hydrocarbon compounds, which fuel has distillation properties of the initial boiling point (initial boiling point 0) in distillation of over 40 C. and 100 C. or lower, the 10 vol. % distillation temperature (T₁₀) of over 50 C. and 120 C. or lower, the 90 vol. % distillation temperature (T₉₀) of 110 C. or higher and 180 C. or lower, and the final boiling point in distillation of 130 C. or higher and 210 C. or lower. The fuel for a fuel cell system has a high power generation quantity per weight, a high power generation quantity per CO₂ emission, a low fuel consumption, a small quantity of evaporative gas (evapo-emission), small deterioration of a fuel cell system comprising such as a reforming catalyst, a water gas shift reaction catalyst, a carbon monoxide removal catalyst, fuel cell stacks and the like to maintain the initial performances for a long duration, good handling properties in terms of storage stability and inflammability, and a low preheating energy.