PURPOSE: To mold a film having excellent quality free from a press flaw, rupture, a scratch, wrinkles or stripes, by setting a polyolefin resin film layer to an inner layer and adding a polyethylene resin having specific density to said inner layer in a specific amount.

CONSTITUTION: A polyolefin resin to which 0.5W70wt.% of a polyethylene resin having density of 0.936g/cm3 or more is added is charged in an extruder 1a while an L-LDPE resin is charged in an extruder 1b and both resins are respectively melted under heating. Next, a polyolefin resin film layer 11 is extruded from the inside slit of a ring die 2 and an L-LDPE resin film layer 12 is extruded from the outside slit of said die 2. At this time, a tubular resin film 6 wherein the film layer 11 is positioned inside and the film layer 12 is positioned outside is molded by the compressed air from a blow pipe 3 and the cooling air from an air ring 4 and rises through a take-over squeeze roll 8, a guide roller 5 and a guide plate 7, and taken up by a take-up roll 9 in such a state that the film layer 11 is brought into contact with said roll 9.