An image reading device includes a contact glass, a first lamp, an image sensor, a first lamp, a light absorbing member, and a second lamp. When reading a document, in a first period, the first lamp is turned on while the second lamp is turned off. In a second period, the second lamp is turned on while the first lamp is turned off. On the basis of first image data obtained by reading in the first period and second image data obtained by reading in the second period, the control unit determines whether each pixel in the first image data is a pixel having read document data or not.