Abstract: A blowbag manufacturing method for manufacturing blowbags made of thermoplastic material and which are used for containing pharmaceuticals, foodstuffs, cosmetics and the like. The blowbag manufacturing method of the present invention, blowmolds a blowbag having a body portion (1) with opposing walls which are flat in section and an opening portion (2) connected to the body portion (1), supports the flat surfaces of the blowmolded blowbag body portion (1) by a pressing surface (8) of a pressing jig (6) having an area smaller than the flat surfaces and so that those flat surfaces are in close contact, and prints required items to an upper surface of those opposing wall surfaces of the body portion (1) in close contact.