A first score line camera captures an image of one sides of a plurality of tablets being conveyed by a conveyor drum. During transfer from the conveyor drum to a first conveyor belt, all the tablets are turned upside down while their directional properties are maintained. A second score line camera captures an image of opposite side of the tablets being conveyed by the first conveyor belt. Based on image data about both the front sides and back sides of the tablets acquired by the first and second score line cameras, a first ink-jet head performs front-side printing process on a front side of a tablet to conform to a predetermined direction relative to a score line in this front side. The second ink-jet head performs back-side printing process on a back side of a tablet to conform to a direction on the back side same as the predetermined direction.