Abstract: To close gaps between workpieces stacked by a robot 2. A movable member 12 is provided to base members 11a, 11b so as to be movable in a stacking direction of the workpieces stacked by the robot. Adjustment members 13a, 13b are stretching in a direction of a stacking area A11 of the workpieces and are provided to the movable member 12 so as to be movable in a direction in which both members are opposing to each other. Adjustment members 14a, 14b are stretching in the direction of the stacking area A11 of the workpieces and are provided to the adjustment member 13a so as to be movable in a direction in which both members are opposing to each other. Adjustment members 15a, 15b are stretching in the direction of the stacking area A11 of the workpieces and are provided to the adjustment member 13b so as to be movable in a direction in which both members are opposing to each other.