To prevent a filter catalyst from being thermally damaged during forced regeneration by reducing the coefficient of thermal expansion of the filter catalyst.

A filter base 1 is impregnated with a liquid combustible substance to form a catalyst layer 2 being a state in which the liquid combustible substance is left penetrated into microcracks 14 of cell partition walls 12, and the liquid combustible substance left in the microcracks 14 is burnt off when the catalyst layer 2 is calcined. Because the catalyst layer component is prevented from penetrating into the microcracks, an increase in the coefficient of thermal expansion can be suppressed.