Provided is a packaging material for electrochemical cells which has an identification mark that can be recognized from the outside and that is difficult to forge. The packaging material comprises a multilayer film which has a structure formed by laminating a base layer (11), an adhesive layer (13), a metal foil layer (12), an acid-modified polyolefin layer (14), and a heat-sealable layer (15) in this order, wherein the base layer (11) comprises both a oriented polyester film (11b) and a oriented nylon film (11e) with a printed layer (11c) provided on the surface of the oriented polyester film (11b) that faces the oriented nylon film (11e).