Electronic device including a plurality of displays and method for operating same

An electronic device is provided. The electronic device includes a housing, a first display slidable through the housing, a portion of the first display being exposed to an outside through the housing, a region of the first display being capable of being changed based on a sliding of the first display through the housing, a second display spaced apart from the exposed portion of the first display and forming a flat surface with the exposed portion of the first display, an optical member positioned on a portion of the second housing associated with the exposed part of the first display; and at least one processor configured to output light through a first portion of the first display associated with the optical member, the light being diffused through the optical member.