PURPOSE: To perform a smooth and accurate feeding of film free from gatherings, skew and waviness by blowing air into folded film with the upper and lower pieces thereof in close contact to form an air layer therebetween and opening the film by an opening member.

CONSTITUTION: Folded film F is fed via a suitable roll 123...123 to a guide roll 106 and thence travels in a direction opposite to an opening member 102, spread largely by a guide roll 104 which separates the film F into the upper piece Fa and the lower piece Fb to guide each of the film pieces to their respective opening members 102 and 102'. Next, an air blow-out device 103 provided between the guide roll 104 and the opening members 102 and 102' gives rise to an air layer E between the upper piece Fa and the lower piece Fb of the film F. With such method, an excessive separation force is not exerted on the film surface when separating the upper piece Fa and the lower piece Fb, without producing gatherings, skew and waviness on the film surface.