Abstract: The present invention provides a heat insulated vessel (A) which is suitable for containing convenience food which can be cooked by hot water, or food or drink which is desired to be eaten or drunk while it is hot, and also a method of producing the vessel. The heat insulated vessel (A) of the present invention is made of a formed product of a foamed synthetic resin. An annular flange is continuous with an opening edge of a bottomed cylindrical portion, and a curled portion which is thinner than the bottomed cylindrical portion and which has a curved section shape is continuous with the annular flange. Preferably, the thickness of the curled portion is 1.5 mm or less.