An apparatus and a method for controlling a screen brightness in a portable terminal, by which consumption of current by the portable terminal can be reduced by reducing the brightness of the display while a screen is being loaded for display. The apparatus preferably includes: a display unit for changing a screen brightness value thereof depending on whether data is operated, and displaying a screen thereof having the changed screen brightness value; and a controller for performing a control operation for changing the screen brightness value while the data is operated, and performing a control operation for causing the changed screen brightness value to return to a screen brightness value before the change when the operation of the data is completed.