PURPOSE: To provide a sealing film which is fused to the opening part of a container by a high frequency induction heating process and is excellent in sealing and unsealing ability and which avoids the danger at the time of fusion by providing the sealing film with a minor diameter part and a major diameter part intersecting the minor diameter part perpendicularly.

CONSTITUTION: A sealing film has at least a high frequency fusing layer formed on its aluminum foil layer and has a minor diameter part 2 and a major diameter part 3 intersecting the minor diameter part 2 perpendicularly. The center of a sealing film 1 is placed over the center of a circular opening part 11 of a container 10 with the center point of the film matching with that of the container opening part. At this time, both the end parts 2a and 2b of the minor diameter part 2 are made to extend from the edge part 12 of the container opening by 0.1-3mm. Both the end parts 3a and 3b of the major diameter part 3 are made to extend longer than the extended end parts 2a and 2b of the minor diameter part 2 by 2-5mm. The extending length of the peripheral film edge 4 is gradually decreased from the end parts 3a and 3b of the major diameter part 3 toward the end parts 2a and 2b of the minor diameter part 2. Therefore, the edge of the major diameter part becomes weaker in fusion than that of the minor diameter part.