To reduce the discharge of toxious and harmful substances in incineration, and to enable mass production at a low cost by processing fibers of reeds, straws, corns, bamboo, etc., into sheets, and pressing them in a die to form a container such as a tray or a pan.

Stock materials to form a product, i.e., fibers of such as reeds, straws, corns, bamboo, kaoliang, kenaf and coconut are changed into knitting or non-woven fabric, and pressed in a die to form a product. Heating and sterilization are performed at the same time. To improve the watertightness, an edible watertight film is attached to the surface. The edible waterproof film includes a gelatin film, a starch film, a polyvinyl alcohol film, and if gelatin film is used, a dried carbohydrate is added by 0.02-0.2% to prevent gelatin from being dissolved with hot water, etc.