An apparatus is improved to successively make plastic bags each of which includes an end surface provided with a spout, by employing the general feeding way of panel material, to be simple in structure, low in cost, high in speed and to make it possible to successively make the plastic bags two by two. A first folded portion is formed in a first web of panel material 1. An aperture is formed in a second web of panel material 2. A spout is inserted into the aperture, the spout and the second web of panel material 2 being heat sealed with each other. The second web of panel material 2 is guided by a guide device 18 to be folded after being heat sealed so that a second folded portion should be formed in the second web of panel material. The spout is turned over by the second folded portion. The second folded portion and the first folded portion are heat sealed with each other while the second folded portion and the second web of panel material 2 are heat sealed with each other about the spout.