A display device and an image forming apparatus capable of reducing discomfort of a worker during maintenance work and improving the work efficiency, are provided. In a copier, an orientation of a display screen of a display device is detected and when the display screen changes its orientation, an image appearing on the display screen changes accordingly. It is determined how the copier is viewed from a worker, and then screen display is performed so that an image appearing on the display device looks the same as the copier which the worker directly sees.