PURPOSE: To neatly cut a film from the center toward both ends with a containing case only by twisting clockwise by a method wherein a cutting member provided at the rim of a lid is made in a sawtooth waveform.

CONSTITUTION: A blade of a cutting member 21 with a sawtooth waveform protruding from the rim of a lid 15 makes an edge C0 having a protruding shape C at the center. A blade 21b of the cutting member 21 which is closest to a bottom side 11a of a case 11 (edge C0 of the protruding shape C) is substantially larger than the other parts 21a of the blade. Blade pitch P1 of this blade 21b and right and left adjacent blades 21a is larger than blade pitch P2 of the other parts of the blade 21a. While tension is applied to a wrap film W by pulling the film in the (+X) direction slightly with the right hand, the left wrist which holds the case 11 is slightly twisted in an arrow α direction (clockwise). This twisting allows the blade 21b of the edge C0 of the cutting member 21 to bite the center of the wrap film W so that the center of the wrap film W can be easily cut.