To provide a portable telephone set with a camera function which can improve the visibility of a display screen even in a bright place without increasing power consumption or the size of the display screen.

The folding portable telephone set with the camera function is provided with at least an open/close detection part 12 for monitoring the open/close state of the folding portable telephone set, a camera part 5 to be started at the time of detecting the open state by the open/close detection part 12, an illuminance detection part 11 for detecting illuminance by using image pickup data inputted by the camera part 5, a character size switching part 9 for switching the sizes of characters to be displayed on the display screen, and a character thickness switching part 10 for switching the thickness of characters. When the illuminance of external light detected by the illuminance detection part 11 is a previously determined reference value and more, the size or thickness of characters to be displayed on a character input picture or a character reference picture is controlled so as to be increased or thickened, so that the visibility of characters displayed on the display part can be surely improved even in a bright place.