An image reading device includes a light source, an imaging element and a control unit. The light source irradiates light on a document. The irradiated light of the light source reflected by the document is incident on the imaging element. The control unit is configured to, if the document is an ordinary document having no light-emitting screen, set a light amount of the irradiated light of the light source at a predetermined reference value and is configured to, if the document is a special document having a light-emitting screen, reduce the light amount of the irradiated light of the light source to become lower than the reference value.