To provide an image forming device where a reader and a printer are designed as separate units and interconnected that can suppress a temperature rise in the inside of the printer even when the reader with a different operating speed is connected to the printer.

In the image reader (image forming device) 1 where a reader section (image reader) 10 is connected to a printer section (image writer) 20, a temperature sensor sensing a temperature of a control circuit board with an internal CPU mounted thereon is provided to the printer section 20 and when the sensed temperature by this temperature sensor exceeds a prescribed value, the image reader 1 inhibits the simultaneous operation of the reader section 10 and the printer section 20 as its control.