Gate blocks 18 are disposed to face each other, wherein the gate blocks 18 include inclined surfaces 18a respectively on inner wall surfaces at an upper end part of a case 7 in which multiple rectangular sheet materials W are stacked with four sides therearound being aligned in a sheet material stocker 3A. An uppermost group of sheet materials W including the uppermost sheet material W are curved so as to project upward, wherein each sheet material of the uppermost group has a predetermined curvature projecting upward. This structure makes it possible that when the uppermost one of the stacked multiple sheet materials W is taken out sequentially by a sheet material take-out means, each sheet material W is reliably taken out sequentially while double take-out of sheet materials is prevented even if each sheet material W has a relatively high rigidity.