A thin type reformer for a fuel cell is provided, and includes a substrate, fuel filling portion, reformer portion, CO remover, and cover. The substrate forms a passage within. The fuel filling portion fills the passage with fuel. The reformer portion forms a passage to one side of the fuel filling portion in the substrate, and the CO remover forms a passage at an opposite side of the fuel filling portion in the substrate. The cover covers the top of the substrate and seals the passages. The fuel filling portion partitions the reformer portion's heat absorbing reaction and the CO remover's heat radiating reaction and induces a reforming reaction. The reacting efficiencies of the reformer portion and the CO remover substantially increase. Because a compact air supplying pump can be used due to an inner pressure reduction in the CO remover, the entire device can be miniaturized.