According to various embodiments, a method of operating an electronic device, which has a foldable housing that causes first and second portions of a display to face each other in a folded state and to be directed in the same direction in an unfolded state and an illuminance sensor that is disposed on a surface on which the second portion is formed, includes a process of determining an angle formed by the first portion and the second portion using data received from an angle detecting sensor; a process of checking out a reference value corresponding to the determined angle in a lookup table; a process of correcting a first illuminance value from the illuminance sensor using the checked reference value; and a process of controlling brightness of the display based on the corrected first illuminance value at least in part.