The invention discloses a skimming device for a bridge-type sand sucker. The skimming device is fixed at the lower parts of the two sides of an operating bridge of the bridge-type sand sucker through an upper bracket; one end of the lower part of the upper bracket is hinged with a skimming rake through a pin shaft, and the other end is hinged with a hook plate; the bottom surface of the hook plate forms a bevel; a triangular outcut is arranged above the bevel; an angle steel is welded on the skimming rake and corresponds to the triangular outcut; a tension spring for drawing and tightening the hook plate and a chain sling for hanging the skimming rake are arranged at the lower part of the upper bracket; and a shedding ejector is fixed at a skimming initial end of a sedimentation tank. During skimming, the skimming rake is hung below the liquid level through the chain sling and climbs along a guide slope at a skimming stroke tail end, so that the angle steel on the skimming rake is automatically hooked in the triangular outcut of the hook plate; during return stroke, the rake bottom is kept being separated from the liquid level as so to prevent floating sludge from being driven to dead corners at the initial end; at a return stroke tail end, the skimming rake is automatically put down by touching of the shedding ejector; and the skimming device has a reasonable structure, is good in automatism, and can remarkably improve the skimming effect.