A numerical key unit 70 mounted in a mounting portion 12 of an image forming apparatus 1 and card reader of inputting information to the image forming apparatus 1 includes a casing 71 mounted on the mounting portion 12, an operating key 100 comprised of a hardware key capable of inputting information on a numerical value, a substrate 73 provided inside the casing 71, a main assembly-side cable 76 connected to a connector 85 mounted on the substrate 73 and electrically connecting the image forming apparatus 1 and the numerical key unit 70, and a first opening 71a through which the main assembly-side cable 76 is inserted. The first opening 71a is provided on a bottom of the casing 71 so that in a thickness direction of the substrate 73, the main assembly-side cable 76 is exposed to an outside of the casing 71 from a surface on a side opposite from a surface where the operating key 100 is provided.