The present invention provides an image reader capable of reading both a paper medium and electronic paper, to provide an image forming apparatus, to provide an electronic paper, and to provide a program. The copying machine 21 comprises an ADF 23 for feeding either of or both the electronic paper and the paper medium to a reading position 80 as a document; an electronic medium detection unit 802which enables a current to flow by bringing a terminal in contact with the document and discriminates a medium class on the basis of whether or not to electrify the document; and an image reader 81 for optically reading an image formed on the paper medium at the reading position 80 or an image switched and displayed on the electronic paper, wherein a controller of the ADF 23 is functioned as a feeding control means for controlling feeding due to the ADF 23 based on the discrimination of the electronic medium detection unit 802 and as a reading control means for controlling reading by the image reader 81.