PURPOSE: A dead support device for reducing velocity of water flow is provided to prevent damage of a river floor by reducing the velocity of the river water and flow the river water from upstream to downstream without congestion. CONSTITUTION: A falling crest weir for reducing velocity of water flow includes a rubble housing box(110), a lower mesh skeleton(120), and a box support(130). The rubble housing box is composed of a concrete. The top and bottom surfaces thereof are opened and the side surfaces are covered to accommodate rubbles(10). The rubble housing box vertically passes through river water. The lower mesh skeleton is formed into a mesh shape in the bottom surface of the rubble housing box. The lower mesh skeleton supports the accommodated rubbles. The box support is projected from the bottom end of the rubble housing box into a bar shape and supports the rubble housing box from the river floor. The box support forms a space where the water river discharged from the bottom of the rubble housing box flows to the downstream.
