The invention relates to the field of sewage treatment, and particularly relates to a skimming device capable of skimming suspended substances such as scum, foam and the like on a liquid level of a horizontal flow sedimentation tank. The skimming device comprises a double-hanging-point hoist, a support seat, a guide device, a sewage collection tank and a scum collection pipe, wherein the double-hanging-point hoist is provided with two cranes, is fixed by the support seat and is connected with the sewage collection tank through the guide device; the scum collection pipe is arranged in the sewage collection tank; the guide device comprises a guide holder, a guide bar and a bushing; the guide bar is installed at the lower part of the double-hanging-point hoist and is fixed by the guide holder and the bushing; and the sewage collection tank and the scum collection pipe ascend or descend through the guide bar.