Method for producing hermetically sealed container for beverage or food

A method for producing a hermetically sealed container for beverage or food by welding a container body and a lid mounted on the mouth portion of the container body according to a laser welding method to achieve an airtight state, wherein the method comprises a process of by:

• using as an intended welding site a sealed portion between an annular rib provided on an outer wall of the mouth portion of the container body of the hermetically sealed container and in parallel to a rim of the mouth portion and an annular ring provided on a rim of the lid of the hermetically sealed container for forming the sealed portion with the rib;
• conveying the container body on which the lid is mounted by a conveyor;
• disposing a laser irradiation apparatus above the conveyor to provide laser light, wherein said apparatus does not move at the same speed as the container body being conveyed by the conveyor;
• irradiating a region where the intended welding site of the container body and the lid inevitably passes through as being moved by the conveyor with laser light that is emitted from an upper side toward a lower side and has an irradiation configuration of being in the form of a region that has a width larger than a minimum width among widths in various directions of the intended welding site, in which the form does not coincide with a configuration of the intended welding site;
• and
• irradiating a region including an entire part of the intended welding site with the laser light by conveying the container with the lid to the laser light irradiation region, so that the entire intended welding site of the container body and the lid is welded when the entire intended welding site passes through the laser light irradiation region.