Abstract: A reformer for a fuel cell is structured so that the entirety of a catalytic layer is effectively used, a sufficient shift reaction is made possible, the volume velocity is raised, and the pressure loss is reduced. The reformer includes a container having an inlet for introduction of a vapor of a methanol solution as a raw fuel, an outlet for discharge of a reformed gas and a catalytic layer in the container. It is structured such that the inside of the container is divided into an inlet space communicating with the inlet and an outlet space communicating with the outlet. A passage cross section of the catalytic layer at a side of the outlet space is larger than a passage cross section at a side of the inlet space, preferably by 20% to 250%.