The embodiment of the invention provides a flexible display device and relates to the display field. All mechanisms are matched to adjust the size of an actual display screen. The flexible display device comprises a flexible display panel and a folding mechanism, wherein the folding mechanism comprises a first shell, a second shell and a guide mechanism, the first shell and the second shell are stacked, and the second shell can move through the guide mechanism relative to the first shell in the linear direction. The flexible display panel further comprises a guide part and an adjusting rod which are located in the second shell, the guide part is located at the push-pull end of the second shell, the adjusting rod can move between the push-pull end and the end opposite to the push-pull end, one end of the flexible display panel is fixed to the push-pull end of the first shell, the other end of the flexible display panel is wound around the guide part and fixed to the adjusting rod in the reverse direction, and a locking mechanism is used for fixing the relative positions of the first shell, the second shell and the adjusting rod.