A display control device capable of suppressing an abrupt change in brightness of a display device viewed by a user when a large change takes place in outside light illuminance, thereby relieving a viewing difficulty. A control unit detects illuminance of outside light irradiated onto the display device, calculates a target brightness value corresponding to the detected illuminance, and sets a brightness setting value for the display device based on the target brightness value. If there is continuity in display content of the display device, the brightness setting value is set while providingan upper limit value for an amount of change in target brightness value. If the display content is changed without continuity, the target brightness value is set as the brightness setting value whileunrestricting the amount of change in the target brightness value.