PURPOSE: To form silica films of desired thickness on the inner surfaces of pores of a catalyst carrier very simply and securely by heating a honeycomb porous silicon carbide sintered material at the given temperature in the oxidation atmosphere.

CONSTITUTION: A base material 1 constituting a catalyst carrier is a porous silicon carbide material having high melting point of approximately 3000°C and is formed in the honeycomb shape. A number of gas permeating pores 2 in parallel extending in the axial direction are formed in said base material 1, and one ends of pores 2 are sealed each other by means of small pieces 3 of silicon carbide. The base material 1 is put into an oven and heated up to approximately 600-1200°C for around 0.3-10 hours while air is fed into forcibly. Then surface layers of silicon carbide crystals are oxidized on the surfaces of inner wall of pores 2 and the surface of the base material 1 to form silica films of specified oxidation degree. Thus, silica films are formed without lowering the strength of the silicone carbide sintered material.