Abstract: This invention provides a fiber filter and a sewage purifier capable of realizing effective use of the capacity of a treatment tank and being easily manufactured. A fiber filter is formed in a manner that ends of a plurality of fibrous materials made of carbon fibers bundled into a fiber bundle are connected to each other at a fixation part. The fiber filter is used as a filter of an anaerobic filter-bed tank of a sewage purifier. A part, which is not fixed at the fixation part, of the fibrous materials of the fiber filter spreads and develops in a tuft shape in sewage. Thus, the surface area of the fiber filter can be increased. Capacity necessary for treatment of the sewage W can be reduced and effectively used. The fiber filter can be easily manufactured due to its simple constitution.