PURPOSE: To obtain the titled film that can be torn easily with fingers in the lateral direction and is useful for spraying cured film etc. by a method wherein the mixture of inorganic filler with ethylene polymer having special physical properties is extruded in the cylindrical form from a circular die and film is prepared at a specific speed and an expansion ratio.

CONSTITUTION: The resin component wherein 10W30wt% of inorganic filler (such as calcium silicate etc.) having an average grain diameter of 0.5W5.0μm is mixed with ethylene polymer having a melt index 1.0gr/10min or less is melted in an extruder, extruded from a circular die D and cooled in cooling gas supplied from a cooling ring to provide a cylinder body 1. Then, this cylinder body 1 is expanded at a expansion starting point N to form a bulb B. At this time, the ratio (DB/DN) of the bulb diameter DB after expansion to the diameter DN of the cylinder body 2 at the expansion starting point N is made eight times the ratio VB/VN of the bulb speed VB after expansion to the speed VN of the cylinder body 2 at the expansion starting point N to obtain the desired film.