A foldable display device may include: a display panel including a first active area, a second active area, and a foldable area between the first active area and the second active area for folding and unfolding the display panel; and a camera in the second active area or overlapping with the second active area. The first active area may be configured to display a test pattern, and the camera may be configured to capture the test pattern to output captured data for compensating a data voltage applied to at least one of the first active area and the second active area of the display panel for displaying an image.