A paste-type dental material is filled from an opening portion of a cartridge into a cylindrical portion by moving the opening portion of the cylindrical portion of the cartridge along a kneading surface, on which the paste-type dental material is kneaded, with the opening portion being inclined. The piston is placed on the kneading surface with a circular end surface of the piston contacting the kneading surface. The piston is inserted into the cylindrical portion by moving the opening portion of the cylindrical portion of the cartridge closer to the piston located on the kneading surface such that a piston-side tapered surface or the piston-side curved surface of the piston is fitted into the opening portion, and thereafter moving the one of the two ends of the cylindrical portion toward the kneading surface.
