A portable electronic device may include: a slidable housing including a first housing and a second housing coupled to the first housing to be slidable with respect to the first housing; a roller unit; a flexible display including a first display area disposed adjacent to the first housing and a second display area disposed in an inner space of the portable electronic device while surrounding the roller unit; a processor connected to the display; and a memory connected to the processor, wherein the memory stores instructions which, when executed, cause the processor to: when a state of the portable electronic device is a first state in which the second display area is disposed in the inner space, determine the first display area as an active area in which visual information is to be displayed, when the state of the portable electronic device is a second state in which the second display area is exposed to the outside, determine, as the active area, an entire area of the display including the first display area and the second display area, display first visual information and a first preview in the active area when the portable electronic device is in the first state, and display second visual information in the active area when the portable electronic device is in the second state. The first preview may be a graphic element for identifying the second visual information. In addition, various embodiments are possible.