A dust collector using a cartridge element, downsized, capable of effectively performing brushing away, and simple in structure and handling. The cartridge element has a flat plate shape as a whole, and is constituted of a flat filter (1) made from a sheet-like filtration material pleated and formed into a tubular shape, a cap (2) and an upper end member (3) that hold openings, perpendicular to the fold lines of the pleats, in a flat plate shape, and a reinforcement member (4) that is a resin pipe or round bar provided laterally across the flat filter (1). All parts used are of a burnable resin.