To provide a bag filter in which peeling of a polytetrafluoroethylene porous membrane hardly occurs in a pleating process or at a time of shaking down dust which is repeatedly practiced on a dust collector.

An air permeable protective layer smoother than an air permeable base is interposed between the polytetrafluoroethylene porous membrane and the air permeable base, these members are laminated and are integrally bonded to each other. Detachment of the polytetrafluoroethylene porous membrane is almost prevented by the existence of the air permeable protective layer, and peeling of the polytetrafluoroethylene porous membrane occurs seldouly at the pleating process or at a time of shaking down the dust.