An apparatus for successively making plastic bags, the apparatus including upper and lower heat seal bars (1H, 1L) between which upper and lower webs of film material (2H, 2L) are directed, upper and lower bodies of zipper material (3H, 3L) being directed between the upper and lower webs of film material (2H, 2L), the webs of film material (2H, 2L) and the bodies of zipper material (3H, 3L) being fed longitudinally thereof and intermittently, a receiver plate being interposed between the upper and lower bodies of zipper material (3H, 3L), the upper heat seal bar being lowered toward the lower heat seal bar whenever the webs of film material (2H, 2L) and the bodies of zipper material (3H, 3L) are fed intermittently and stopped temporarily so that the webs of film material (2H, 2L) and the bodies of zipper material (3H, 3L) are sandwiched between the heat seal bars (1H, 1L) and the receiver plate, the upper web of film material and the upper body of zipper material being heat sealed with each other while the lower web of film material and the lower body of zipper material are heat sealed with each other, to successively make the plastic bags of the webs of film material (2H, 2L) and the bodies of zipper material (3H, 3L), the apparatus comprising: a support plate extending widthwise of the webs of film material (2H, 2L) to protrude on one of opposite sides of the webs of film material (2H, 2L), the receiver plate being fixed to the support plate; the apparatus being characterised by an elastic support device disposed on the one side of the webs of film material (2H, 2L) and interposed between the support plate and a frame to elastically support the receiver plate and the support plate so that the receiver plate and the support plate are pushed down and lowered by the upper heat seal bar to make the webs of film material (2H, 2L) and the bodies of zipper material (3H, 3L) sandwiched between the heat seal bars (1H, 1L) and the receiver plate and heat sealed with each other, the receiver plate and the support plate being raised by the elastic support device so that the receiver plate is moved away from the lower heat seal bar after the webs of film material (2H, 2L) and the bodies of zipper material (3H, 3L) are heat sealed with each other; and an attitude hold device disposed on the one side of the webs of film material (2H, 2L) and interposed between the support plate and the frame to act on the support plate so that the receiver plate and the support plate are held in attitude not to be inclined when being lowered and raised. a support plate extending widthwise of the webs of film material (2H, 2L) to protrude on one of opposite sides of the webs of film material (2H, 2L), the receiver plate being fixed to the support plate; the apparatus being characterised by an elastic support device disposed on the one side of the webs of film material (2H, 2L) and interposed between the support plate and a frame to elastically support the receiver plate and the support plate so that the receiver plate and the support plate are pushed down and lowered by the upper heat seal bar to make the webs of film material (2H, 2L) and the bodies of zipper material (3H, 3L) sandwiched between the heat seal bars (1H, 1L) and the receiver plate and heat sealed with each other, the receiver plate and the support plate being raised by the elastic support device so that the receiver plate is moved away from the lower heat seal bar after the webs of film material (2H, 2L) and the bodies of zipper material (3H, 3L) are heat sealed with each other; and an attitude hold device disposed on the one side of the webs of film material (2H, 2L) and interposed between the support plate and the frame to act on the support plate so that the receiver plate and the support plate are held in attitude not to be inclined when being lowered and raised.