Abstract: A packaging machine has belts for clamping both side edges of a film pulled out selectably from either of two film rolls and transporting it accordingly in either direction to a packaging station. Its film supplying apparatus includes a plurality of sensors capable of detecting both presence and absence of a film. They are disposed at both ends of the belts and each sensor is adapted to output a warning signal when either the presence or absence of a film is detected thereby, depending whether it is at the downstream or upstream end of the belt with respect to the direction of film being transported thereby.