To reuse a ceramic-made filter while filtering and adsorption efficiency are improved by suppressing a drop of a strength by a method wherein an active carbon having a carbon atom as a skeleton is formed in a fine particle as a pore material, used, and the carbon and another preparation are degreased and burnt to form a filter which is dense having a great pore area.

Kaoline clay miniral, porous inorganic substance, and fine particle active carbon are mixed in porcelain clay or the like as a raw material, and further organic binder is added thereto. Then the mixture is made into a filter product via wet preparation, degreasing and burning processes. At that time a burning temperature and a treating time are determined based on a time point of burning completion time of granular active carbon used in order to raise an effective porosity, and a Mohs' hardness to be obtained. That is, the burning temperature is within a range of 500 to 1,200°C, Mohs' hardness is at most 6, and the pore diameter is 0.1 to 20 μm. For this filter, a performance can be improved according to a high porosity to be generated after burning a finely granular active carbon. Further, since the Mohs' hardness is set low, if a surface layer is uniformly shaved off, it can be also reused.