A housing of an electronic device according to an embodiment may include a combination of at least two housings, and the entire size or length of the electronic device may change according to relative movement between the housings. The electronic device may comprise: a flexible display configured to expand or contract according to a change in size of the electronic device. A portion of the flexible display may be inserted into the housing when the housing contracts and may be drawn out of the housing when the housing expands. The electronic device may comprise a distance sensor and/or an expansion sensor. The distance sensor is configured to measure a change in a relative distance of the housing, and the expansion sensor senses a contraction or expansion state of the housing, thereby contributing to correcting data measured by the distance sensor. The electronic device employing the distance sensor and/or the expansion sensor can accurately sense the size of an externally visible portion of a display and can display a screen appropriate to the size of the visible portion of the display.