Abstract: An automatic carton forming device includes a supporting table, a storage rack, a limiting part, a transporting part, and a folding part. The storage rack is configured to store folded paper boards, the limiting part is configured to limit the folded paper boards, the transporting part includes a moving base and a driving unit for driving the moving base to move. At least one first vacuum suction cup is disposed on the moving base, the limiting part includes an adsorbing base disposed on one end of the supporting table, at least one second vacuum suction cup is disposed on the adsorbing base. The folding part includes a first overturning plate, a vertical folding unit, a transverse folding unit, and a transmitting unit, and the transmitting unit drives the first overturning plate, the vertical folding unit, and the transverse folding unit to perform folding action.