A foldable display device includes a display screen including a first half screen and a second half screen, a controller and at least one angle probe set. Each set includes a transmitter and a plurality of receivers. The transmitter is inclined at a first angle with respect to the first half screen and faces the second half screen, and is configured to emit collimated infrared light. Each receiver is inclined at a second angle with respect to the second half screen, and is in signal connection with the controller, and is configured to transmit an electrical signal to the controller when receiving the collimated infrared light. The controller is in signal connection with the display screen, and is configured to determine a bending angle from angle information of the receiver and control the display screen to switch to a display state for the bending angle.