An apparatus for successively making plastic bags each of which includes an end surface provided with a spout, the apparatus comprising: a feeding device by which a wide web of panel material can be fed longitudinally thereof and intermittently; an aperture forming device by which an aperture can be formed in the wide web of panel material at a position predetermined widthwise of the wide web of panel material when the wide web of panel material is stopped temporarily; a spout inserting device by which a spout can be inserted into the aperture; a spout seal device by which the spout and the wide web of panel material can be heat sealed with each other when the wide web of panel material is stopped temporarily; a guide device, located downstream of the spout seal device, by which the wide web of panel material can be guided so that the wide web of panel material can be folded and folded back along a first longitudinal folded line and a longitudinal folded back line extending between one side edge and the spout when the wide web of panel material is fed so that a first folded portion and a folded back portion can be formed in the wide web of panel material, the wide web of panel material being folded along a second longitudinal folded line extending at a position predetermined widthwise of the wide web of panel material so that a second folded portion is formed in the wide web of panel material, the spout being turned over by the second folded portion, the spout and the longitudinal folded back line being positioned between the first and second longitudinal folded lines (51, 55); and a circumferential seal device by which the second folded portion and the first folded portion can be heat sealed with each other while the second folded portion and the wide web of panel material are heat sealed with each other about the spout when the wide web of panel material is stopped temporarily, so that the end surface can be formed by the second folded portion provided with the spout. a feeding device by which a wide web of panel material can be fed longitudinally thereof and intermittently; an aperture forming device by which an aperture can be formed in the wide web of panel material at a position predetermined widthwise of the wide web of panel material when the wide web of panel material is stopped temporarily; a spout inserting device by which a spout can be inserted into the aperture; a spout seal device by which the spout and the wide web of panel material can be heat sealed with each other when the wide web of panel material is stopped temporarily; a guide device, located downstream of the spout seal device, by which the wide web of panel material can be guided so that the wide web of panel material can be folded and folded back along a first longitudinal folded line and a longitudinal folded back line extending between one side edge and the spout when the wide web of panel material is fed so that a first folded portion and a folded back portion can be formed in the wide web of panel material, the wide web of panel material being folded along a second longitudinal folded line extending at a position predetermined widthwise of the wide web of panel material so that a second folded portion is formed in the wide web of panel material, the spout being turned over by the second folded portion, the spout and the longitudinal folded back line being positioned between the first and second longitudinal folded lines (51, 55); and a circumferential seal device by which the second folded portion and the first folded portion can be heat sealed with each other while the second folded portion and the wide web of panel material are heat sealed with each other about the spout when the wide web of panel material is stopped temporarily, so that the end surface can be formed by the second folded portion provided with the spout.