a laminated non - woven fabric for filtering medium , which is composed of a plurality of non - woven fabric layers having different average pore sizes and laminated in the order of the average pore size , and a plurality of entangled regions interposed between any of adjacent two non - woven fabric layers which is formed by causing fibers of one of the adjacent two non - woven fabric layers to penetrate into the other layers to entangle the penetrated fibers with fibers of the other layers . the presence of the entangled regions provide a gradual change of the pore size from a non - woven fabric layer to another non - woven fabric layer to result in a good filtering efficiency and an elongated lifetime of a filter .