To make it possible to form high-quality film without cracks on a honeycomb matrix of high passageway density by applying a soft film inside of porous inorganic monolithic substrate provided with penetrating passageways, and applying pressure to the film to bond the film to the substrate.

A substrate is a monolithic object to pass fluid, which is any side and shape dependent on usage, for example, of ceramic, glass ceramic, glass, metal, and combination of them. Coating martial is preferably polymeric material applied to the inside of the passageways of the substrate as a thin film. Fusing or bonding of film to the inner passageways of the substrate can be performed using any technique for making adhering condition for adhering by applying pressure of a certain extent. For example, by heating the coating material and/or substrate for softening the polymer film, the fusing can be performed.