To maintain the airtightness even when the upside of the open side rim of a pot main body takes a flaw, by a method wherein protruding pieces are formed along the circumference of a lid at intervals, connecting claws to be connected to the protruding pieces are formed along the circumference of an opening of the pot main body at intervals, and an elastic packing to come in contact with the inner circumference of the opening of the pot main body is arranged on the lid.

Protruding pieces 4 are formed along the circumference of a lid 2 at intervals, and connecting claws 5 that have a nearly U-shaped cross section and are to be connected to the protruding pieces 4 are formed along the circumference of an opening of a pot main body 1. A cylindrical part 6 with an annular groove 8 on the outer circumferential face is formed on the downside of the lid 2 and an annular packing 7 is arranged around the cylindrical part 6. A protruding band 9 that is fitted in the groove 8 is formed on line inner circumferential face of the packing 7. Thereby, the packing 7 is attached out the cylindrical part 6 in immovable state. When a pressure cooking pot is used, the lid 2 is put on the pot main body 1 so as to locate the protruding pieces 4 of the lid 2 between the connecting claws of the pot main body 1, turned in the one direction to insert the protruding pieces 4 in the connecting claws 5 and then locked.