A luminance control device and method are disclosed. A surrounding brightness of a touch panel is measured to obtain a measured surrounding brightness. A luminance of the touch panel is controlled during a first time period starting from when the measured surrounding brightness changes from a first condition to a second condition, during which the measured surrounding brightness decreases by an amount equal to or greater than a threshold value. The luminance of the touch panel is maintained at a first luminance corresponding to the first condition when the measured surrounding brightness changes from the second condition to the first condition. The luminance of the touch panel is controlled to change to a second luminance corresponding to the second condition, when the measured surrounding brightness has not changed from the second condition to the first condition.