In a method of manufacturing an exhaust gas purifying filter that captures and purifies particulates involved in an exhaust gas emitted from an internal combustion engine, a honeycomb mold body of a desired length is firstly made by an extrusion molding step. In a sealing and enlarging step, tapered front parts of a multi-taper jig are inserted into the corresponding openings of the cells. The multi-taper jig is then oscillatory moved in a direction perpendicular to a longitudinal length of the ceramic mold body while heating the partition walls forming the cells, so that the opening of one cell is closed and sealed completely and the opening of the adjacent cell is enlarged in area. Finally, the honeycomb mold body is burned.