PURPOSE: To obtain a hollow tray which is inexpensive, excellent in heat insulation and disposability by a method wherein two sheets of film are placed in superposition and are bonded together linearly at least on one part corresponding to the border between the bottom face and the side face of the tray, and nonbonded parts between the two sheets are inflated to form a hollow tray.

CONSTITUTION: Two sheets of film are placed in superposition and are bonded together linearly by heat sealing at least on a part A corresponding to the border between the bottom face and the side face of a tray and a part B corresponding to the border between the side face and the flange part of the tray. The bonding is made partially so that an injection port C for gaseous body can be provided. As occasion demands, bonded parts D may be made on the bottom face of the tray for providing reinforcing ribs thereto. Nonbonded parts between the two sheets are filled with gas injected through the injection port C and the nonbonded parts are inflated therewith. Thereby, the two sheets of film can be endowed with rigidity, and by sealing up the injection port C by heat sealing after the inflation, the objective hollow tray can be obtained.