[Object] To provide a multilayer assembly that excels in pore properties, is flexible, and is satisfactorily handled and processed; and a method of producing the multilayer assembly.[Solving Means] A multilayer assembly includes a base and, arranged on at least one side thereof, a porous layer and has a large number of continuous micropores with an average pore diameter of 0.01 to 10 μm. The multilayer assembly suffers from no interfacial delamination between the base and the porous layer when examined in a tape peeling test according to the following procedure: Tape Peeling Test A 24-mm wide masking tape [Film Masking Tape No. 603 (#25)] supplied by Teraoka Seisakusho Co., Ltd. is applied to a surface of the porous layer of the multilayer assembly and press-bonded thereto with a roller having a diameter of 30 mm and a load of 200 gf to give a sample; and the sample is subjected to a T-peel test with a tensile tester at a peel rate of 50 mm/min.