PROBLEM TO BE SOLVED: To provide a sealing structure for sealing the upper end opening portion of a plastic container for culturing mushrooms. SOLUTION: One side and the other side of the upper end opening portion 12 of a container for culturing mushrooms are covered with plastic films 22, 24, respectively. The peripheral portions of the two films 22, 24 are heated and press-adhered to the periphery 122 of the upper end opening portion of the container for culturing the mushroom. The mutually facing inside edges 222, 242 of the two films 22, 24 are superposed on each other, and gas flow passages 40 for allowing the atmosphere on the outside of the films 22, 24 to communicate with a gas in a space on the inside of the container 10 for culturing the mushroom are formed between the inner side edges 222, 242 of the superposed films.
