A flexible display device includes a flexible display panel bendable along a bending axis. A support backplate is disposed on a side of the flexible display panel and located on an outer side of the flexible display panel when bending. The support backplate includes a support area and a plurality of extension areas defined on opposite sides of the bending axis and adjoining two sides of the support area. When the flexible display device is in an expanded state, a difference value between a length of the support backplate and a length of the flexible display panel in a direction perpendicular to the bending axis is greater than or equal to a first threshold. The flexible display device can reduce the risk of peeling of components in a bent state and can ensure a product lifespan.