A flexible organic light emitting device includes a flexible substrate, an organic light emitting unit and a covering substrate. The organic light emitting unit includes a first electrode layer, a second electrode layer opposing the first electrode, and a light emitting layer, which is disposed between the first and second electrode layers. The covering substrate includes a base film, an insulation layer and an adhesion layer. An inner surface of the base film is facing an inner surface of the flexible substrate, and space is formed there-between. The insulation layer is disposed on the inner surface of the base film, and an adhesive force between the insulation layer and the organic light emitting unit is less than 0.1 N/cm. The adhesion layer is disposed between the insulation layer and the inner surface of the base film, covers the insulation layer and the organic light emitting unit, and fills the space.