A lampshade structure for LED lamps includes at least one light-diffusing bowl structure, a lower end, an interior space and a sidewall. The light-diffusing bowl structure composed by an exterior curve wall and an interior curve wall is located on top of the lampshade to diffuse lights from the LED laterally to the lamp. Both the curvature centers of the exterior curve wall and the interior curve wall are located exteriorly to the lampshade structure. By providing the concave light-diffusing bowl structure to occupy the illumination angle of the LED, the incident rays of the LED to the bowl structure can be partly deflected to leave from the lateral sides of the lampshade so as to emulate the LED lamp as an omni-directional lamp device.