PURPOSE: To prevent an improper film from being loaded into a sealer for preventing troubles such as lost addresses, cut documents, jams, etc.

CONSTITUTION: A film type identifying mark Km and a cut positioning mark Cm are provided with a predetermined positional relation on a deposition area SA of one of roll films 11a. A mark detecting means is provided at a predetermined position of a film transfer path corresponding to the deposition area, wherein a pattern of a signal waveform obtained from a detection signal from the mark detecting means is checked against a reference pattern stored in advance for a predetermined film type for automatically detecting whether the film is proper or improper based on whether or not the marks match. If the checking of the signal waveform pattern obtained from the mark detecting means against the reference pattern results in matching, sealing is continued. In the case of not matching, sealing is inhibited. Based on the detection that the marks do not match, an alarm is issued and displayed, and a prompt for a proper film loading is displayed.