PURPOSE: To control the degree of crosslink of each layer in a multi-layered film to improve characteristics such as heat-sealing properties, tensile-shear strength, glossiness, and others by a method wherein a lamination film consisting of layers containing specific one or more substances by the amount different from the content in adjacent layers is crosslinked by an ionizing radiation.

CONSTITUTION: A group A includes a hydrogenated petroleum hydrocarbon resin, a hydrogenated terpene resin, a terpene resin, a rosin, a rosin derivative, coumarone- indene resin, an aliphatic petroleum hydrocarbon resin, and an aromatic petroleum hydrocarbon resin. By using one or more substances selected from among the group A, the gradient in the arrangement of the degrees of crosslink of respective layers forming a lamination film is adjusted. An ethylene resin-crosslinked lamination film is obtained by crosslinking the lamination film by an ionizing radiation; in the lamination film, one or more substances selected from among the group A is contained in at least one layer, and the layer has the content of the substance different from that of the other adjacent layers. The irradiation of the ionizing radiation is performed in the condition that at least one substance selected from among the group A is incorporated in at least one layer of the lamination material, whereby the ethylene resin- crosslinked lamination film is produced.