Rainwater drainage device for building roof

The utility model discloses a building roof rainwater drainage device, which belongs to the technical field of roof drainage and comprises a house body, a rainwater storage room is arranged at the rear end of the house body, a settling pond is arranged on the upper side in the rainwater storage room, a temporary storage cavity is arranged on the lower side of the settling pond, and a rainwater containing cavity is arranged on the lower side of the temporary storage cavity. The filtering assembly is arranged, the filtering plate is placed at the upper ends of the water receiving grooves, meanwhile, the folded plates are in lap joint with the upper sides of the two ends of the house body, then the fixing bolts penetrate through the folded plates, and the fixing bolts are screwed into the fixing holes in the side edges of the house body, so that the effect of fixing the folded plates is achieved; the folded plate supports the filter plate through the inclined rod and the supporting rod, the filter plate filters