Easy-open container, manufacturing method thereof and manufacturing device thereof

An easy-open container, comprising:

• a container body having an opening and a flange extending from a circumference of the opening;
• and
• a lid for covering the opening, a surface layer of the container body exposed on the flange and a seal layer of the lid being circularly heat-sealed to form the easy-open container, wherein
• the lid is configured to be opened by a cohesive failure occurring in at least one of the surface layer of the container body and the seal layer of the lid,
• a swelling first gathered resin part formed of respective resin components of the surface layer of the container body, a layer adjacent to the surface layer and the seal layer of the lid is formed in a vicinity of an inner circumferential end of a seal part located on the flange, and
• an outer circumferential end of the seal part at an open trigger is flat or defines a smaller second gathered resin part smaller than the first gathered resin part in the vicinity of the inner circumferential end of the seal part.