PURPOSE: To obtain a cell immobilizing material having large supporting capac ity by forming a carbon porous body having bulk density of 0.05 to 0.5g/cm3, carbon content of 85 to 95% and a specific surface area of 100m2/g or more by successively applying carbonization and activation treatments to a phenol resin foamed body.

CONSTITUTION: Pref., a resole type phenol resin (obtained by the reaction of phenols and aldehydes in the presence of an alkali catalyst) is foamed and cured pref. using an evaporation type foaming agent (paraffinic hydrocarbon) and a curing agent (sulfuric acid or hydrochloric acid). Further, a viscosity controller or a filler is added to said resin if necessary and the molded body of the obtained phenol resin foamed body is baked and carbonized to obtain a carbon porous body. Further pref., the carbonized body is subjected to activa tion treatment under an oxidable gaseous atmosphere to make it possible to obtain a carbon porous body having properties such that bulk density is 0.05 to 0.5g/cm3, carbon content is 85 to 95% and a specific surface area is 100m2/g or more and excellent in cell supporting capacity and treatment capacity due to org. component adsorbing capacity.