A stack holding apparatus comprising a stacking platform on which sheet members are stacked, a pressing mechanism constantly pressing the stacking platform toward an upper side in the stacking direction of the sheet members stacked on the stacking platform, a pair of clamp rods arranged in parallel with a front-back direction of the stacking platform so as to face the two left and right sides of the stacking platform, clamp arms fixed to the clamp rods and clamping the sheet members stacked on the stacking platform from an upper side in the stacking direction, slide mechanisms making the clamp rods move parallel to the stacking direction, and tilt mechanisms making the clamp rods tilt so that the clamp arms open to an upper side in the stacking direction while moving away from the stacking platform and further so that the clamp arms approach the stacking platform while closing to the lower side in the stacking direction.