Disclosed are an electronic device including a flexible display, and an operation method thereof. The electronic device may include a battery for power supply, a display unit, and at least one processor. The display unit may include at least one flexible display. As a state of the electronic device switches from a first state to a second state, a screen display area among a display area of the display unit may change from a first area to a second area. In the first state, a first indicator relating to a battery residual capacity identified according to the size of the first area may be displayed through the first area. In the second state, a second indicator relating to a battery residual capacity identified according to the size of the second area may be displayed through the second area.