Such a displaying device that can be easily operated by aged persons and handicapped persons, and an image forming apparatus using the same will be provided. Upon continuously operating an upper button for the predetermined period of time, a set value of a magnification is changed at intervals of numeric change that are different from each other between a voice guide mode activated by a voice guide button and a normal mode. At this time, it is configured in such a manner that the interval of numeric change for the normal mode is smaller than the interval of numeric change for the voice guide mode, i.e., the changing rate of the set value of the magnification for the normal mode is larger than that for the voice guide mode.