A shading device for being arranged in association to a window includes an elongated guide rail arrangement that is adapted to be stationarily arranged relative to the window, an extendable covering, at least one elongated support member and a movement arrangement. The extendable covering is supported by the at least one elongated support member, wherein the at least one elongated support member is arranged to extend with its longitudinal direction in a transverse orientation relative to a longitudinal direction of the elongated guide rail arrangement and arranged to be movable along the elongated guide rail arrangement in the transverse orientation by the movement arrangement so that the extendable covering may be moved between a retracted state and an extended state for covering the window to different extents.