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 first and second webs of panel material (1, 2) can be disposed along a horizontal plane and fed longitudinally thereof and intermittently, a first guide device located upstream of the feeding device by which the first web of panel material can be folded along a first longitudinal folded line extending adjacent to one side edge so that a first folded portion is formed in the first web of panel material, guide rollers located downstream of the first guide device and upstream of the feeding device by which the second web of panel material can be superposed with the first web of panel material on opposite side to the first folded portion to have one side edge protruding beyond the first longitudinal folded line at a distance; an aperture forming device by which apertures can be formed in the second web of panel material at positions between the one side edge of the second web of panel material and the first longitudinal folded line when the first and second webs of panel material (1, 2) are stopped temporarily; a spout inserting device by which spouts can be inserted into the apertures; a spout seal device by which the spouts and the second web of panel material can be heat sealed with each other when the first and second webs of panel material (1, 2) are stopped temporarily; a second guide device, located downstream of the spout seal device, by which the second web of panel material can be guided to be folded along a second longitudinal folded line extending between the spouts and the first longitudinal folded line when the first and second webs of panel material (1, 2) are fed so that a second folded portion can be formed in the second web of panel material, the spouts being turned over by the second folded portion, the second folded portion being superposed with the first folded portion; 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 second web of panel material can be heat sealed with each other about the spouts when the first and second webs of panel material (1, 2) are stopped temporarily, such that the end surface can be formed by the second folded portion provided with the spout. a feeding device by which first and second webs of panel material (1, 2) can be disposed along a horizontal plane and fed longitudinally thereof and intermittently, a first guide device located upstream of the feeding device by which the first web of panel material can be folded along a first longitudinal folded line extending adjacent to one side edge so that a first folded portion is formed in the first web of panel material, guide rollers located downstream of the first guide device and upstream of the feeding device by which the second web of panel material can be superposed with the first web of panel material on opposite side to the first folded portion to have one side edge protruding beyond the first longitudinal folded line at a distance; an aperture forming device by which apertures can be formed in the second web of panel material at positions between the one side edge of the second web of panel material and the first longitudinal folded line when the first and second webs of panel material (1, 2) are stopped temporarily; a spout inserting device by which spouts can be inserted into the apertures; a spout seal device by which the spouts and the second web of panel material can be heat sealed with each other when the first and second webs of panel material (1, 2) are stopped temporarily; a second guide device, located downstream of the spout seal device, by which the second web of panel material can be guided to be folded along a second longitudinal folded line extending between the spouts and the first longitudinal folded line when the first and second webs of panel material (1, 2) are fed so that a second folded portion can be formed in the second web of panel material, the spouts being turned over by the second folded portion, the second folded portion being superposed with the first folded portion; 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 second web of panel material can be heat sealed with each other about the spouts when the first and second webs of panel material (1, 2) are stopped temporarily, such that the end surface can be formed by the second folded portion provided with the spout.