An electronic device operating method according to various embodiments of the present disclosure can measure the external temperature of the electronic device by using at least one sensor module. The method can calculate, from the whole area of a flexible display, a fixed area visually exposed to the outside regardless of the screen size of the electronic device, and a variable area having at least a part visually exposed to the outside in a screen expansion or screen size change state of the electronic device. The external temperature is compared with a preset first critical temperature so that heating of the variable area can be determined if the external temperature is less than the first critical temperature. The variable area can be heated by controlling the brightness of the variable area and/or driving frequency.