To provide a display device in which the direction of the image displayed to a display means of electronic paper is controlled to be in a direction that facilitates image to be visible by a user without need for the user making a specific operation, and to provide an electronic paper and an output unit.

Whether the electronic paper 5 is bound by a short side or by a long side is detected in a master paper. When the binding is by the short side, the image data of the even pages of the content is rotated 180 in the master paper. Then, the image data after the rotation is transmitted to a slave paper. In the slave paper, therefore, the image of the different directions can be displayed in a front display element 51 and a rear face display element 52, simply by making the image data, attached to a command from the master paper on the front display element 51 or the rear face display element 52, displayed.