A foldable display device, comprising: a first body configured to support a first display screen; a second body configured to support a second display screen, wherein the first display screen and the second display screen are provided at a first side of the foldable display device, the first body is further configured to support a third display screen, and the third display screen is provided at a second side, which is the opposite side of the first side; an angle sensing unit configured to sense a folding angle between the first body and the second body, wherein the first body and the second body are foldable in a direction to which the first display screen and the second display screen are facing; a first illuminance sensing unit provided in the first side configured to sense illuminance; a second illuminance sensing unit provided in the second side configured to sense illuminance; and a processor configured to control the first display screen, the second display screen, the angle sensing unit, the first illuminance sensing unit and the second illuminance sensing unit, characterized in that the processor is further configured to: adjust the illuminance of at least one of the first display screen and the second display screen based on a first illuminance value detected by the first illuminance sensing unit when the folding angle is equal to a prescribed first angle or greater than the prescribed first angle; adjust the illuminance of at least one of the first display screen and the second display screen based on a second illuminance value detected by the second illuminance sensing unit when the folding angle is smaller than the prescribed first angle; adjust the illuminance of the third display screen based on the second illuminance value; wherein if the angle as sensed by the angle sensor is substantially equal to 0 degrees, the controller is configured to control the first illuminance sensing unit not to perform illuminance detecting; and wherein if the sensed angle is substantially equal to 180 degrees, the controller controls the second illuminance sensing unit not to perform illuminance detecting. a first body configured to support a first display screen; a second body configured to support a second display screen, wherein the first display screen and the second display screen are provided at a first side of the foldable display device, the first body is further configured to support a third display screen, and the third display screen is provided at a second side, which is the opposite side of the first side; an angle sensing unit configured to sense a folding angle between the first body and the second body, wherein the first body and the second body are foldable in a direction to which the first display screen and the second display screen are facing; a first illuminance sensing unit provided in the first side configured to sense illuminance; a second illuminance sensing unit provided in the second side configured to sense illuminance; and a processor configured to control the first display screen, the second display screen, the angle sensing unit, the first illuminance sensing unit and the second illuminance sensing unit, characterized in that the processor is further configured to: adjust the illuminance of at least one of the first display screen and the second display screen based on a first illuminance value detected by the first illuminance sensing unit when the folding angle is equal to a prescribed first angle or greater than the prescribed first angle; adjust the illuminance of at least one of the first display screen and the second display screen based on a second illuminance value detected by the second illuminance sensing unit when the folding angle is smaller than the prescribed first angle; adjust the illuminance of the third display screen based on the second illuminance value; wherein if the angle as sensed by the angle sensor is substantially equal to 0 degrees, the controller is configured to control the first illuminance sensing unit not to perform illuminance detecting; and wherein if the sensed angle is substantially equal to 180 degrees, the controller controls the second illuminance sensing unit not to perform illuminance detecting. adjust the illuminance of at least one of the first display screen and the second display screen based on a first illuminance value detected by the first illuminance sensing unit when the folding angle is equal to a prescribed first angle or greater than the prescribed first angle; adjust the illuminance of at least one of the first display screen and the second display screen based on a second illuminance value detected by the second illuminance sensing unit when the folding angle is smaller than the prescribed first angle; adjust the illuminance of the third display screen based on the second illuminance value; wherein if the angle as sensed by the angle sensor is substantially equal to 0 degrees, the controller is configured to control the first illuminance sensing unit not to perform illuminance detecting; and wherein if the sensed angle is substantially equal to 180 degrees, the controller controls the second illuminance sensing unit not to perform illuminance detecting.