The present invention provides a fuel treatment device which can realize easy separation and collection of a catalyst contained in the device. In a fuel treatment device (21) of the present invention a fuel gas is supplied to a catalyst, which fills a catalyst filling space (24) surrounded by a cylindrical inner circumferential wall and a cylindrical outer circumferential wall, to produce a reformed gas. The fuel treatment device (21) has a removal section indicator indicating a catalyst removal section (29) on the outer circumferential surface of the outer circumferential wall of the cylindrical catalyst filling space (24) and an opening formation assister assisting the formation of a catalyst removal opening for removing the catalyst. The removal section indicator and the opening formation assister are, for example, an oval annular shallow groove (30) formed at the outer circumferential wall of the catalyst filling space (24) over substantially the entire length in the axial direction of the catalyst filling space (24). When a catalyst (25) is collected from the fuel treatment device (21) after a lapse of a period of use, the catalyst removal opening (29) surrounded by the annular shallow groove (30) is cut off, and a catalyst removal opening (40) is formed.