stacked on carrying plate 41 the front end thereof is relatively slid with respect to the arc slope of the arc segment of the carrying plate 41 since the pressure exerted by the elastic pressing sheet 422 is increased therefore the resistance exerted on the sheet medium subsequently conveyed out is increased therefore the force acted on the accumulating portion blocking plate 421 by the sheet medium when it is collided with the accumulating portion blocking plate and the counter force of the accumulating portion blocking plate 421 are reduced finally the sheet medium is stopped at the tail end of the carrying plate 41 in this case if the surface of the arc slope of the arc segment of the carrying plate 41 is relatively smooth it has the same effect as that in which the sheet medium has a larger stiffness and a relatively smooth surface as shown in fig1 in a case that the sheet medium has a small stiffness when it is conveyed to the sheet medium stacking device 4 the deformation of the elastic pressing sheet 422 is small since the sheet medium is prone to be deformed and the front end of the sheet medium is relatively close to the carrying plate 41 therefore the sheet medium is moved along the direction of the elastic pressing sheet 422 and becomes in contact with the carrying plate 41 earlier meanwhile the sheet medium is slid on the carrying plate 41 at a larger distance which thereby largely reduces the speed of the sheet medium since the stiffness of the sheet medium is small it is easier for the sheet medium to slide forward close to.