According to example embodiments, an automatic packing apparatus includes at least one box supply unit configured to move a box stack upwards such that a product is inserted into a packing box of the box stack, the packing box being the uppermost box of the box stack, an inlet formation unit configured to lift the upper surface of the packing box to form an inlet on at least one unbonded side surface of the packing box, a product supply unit configured to transfer the product to the inlet; and a side surface bonding unit configured to bond the at least one unbonded side surface of the packing box. The at least one unbonded side surface includes the inlet and the packing box includes the product inserted therein.