A treatment-object modifying device lowers a pH value of a surface of a treatment object by using dielectric-barrier discharge. The treatment-object modifying device includes discharge electrodes disposed over a conveying route of the treatment object; and a counter electrode disposed to face the discharge electrodes across the conveying route so as to correspond to the respective discharge electrodes. Each discharge electrode has a columnar shape or a cylindrical shape. Curved surfaces of the discharge electrodes faces the counter electrode. Curved surfaces of the discharge electrodes face one another. A distance between the adjacent discharge electrodes is equal to or less than 2 millimeters.