Disclosed herein is a flexible display device having a bending sensing device configured such that an external resistor is mounted in the flexible display device together with a bending sensor, whereby it is possible to lower an output offset voltage, to reduce resistance deviation depending on temperature change, and to sense twisting of the flexible display device. The bending sensing device includes at least one bending sensor mounted in a bending region of a film (layer) that is tensioned and/or a film (layer) that is compressed when the flexible display device, including a plurality of films (layers), is bent and at least one reference resistor mounted in a non-bending region of the film (layer) that is tensioned and/or the film (layer) that is compressed.