Abstract: A storage container with improved strength and airtightness, and a method for manufacturing the storage container are provided. The storage container includes, as a functional resin member, an insert component for a container body insert-molded with a molding material containing predetermined resin. The functional resin member is a side wall plate with support pieces. The side wall plate has a thick portion having at least a thickness of a side wall of the container body, and a thin joint portion formed around the thick portion, to be interposed into and joined to a peripheral wall of the container body. Most of the peripheral wall and the thin joint portion are engaged and joined to enlarge their contact area to eliminate a decrease of the mechanical strength and leakage around the peripheral edge of the side wall plate and prevent the peripheral wall from parting from the side wall plate.