The invention discloses a water draining device. The water draining device comprises a steam pipe, a U-shaped water seal pipe, a water draining box and a hollow container. A water draining outlet of the steam pipe is connected with an inlet of the U-shaped water seal pipe. An outlet of the U-shaped water seal pipe is connected with the hollow container. The hollow container is connected with an inlet and an outlet of the water draining box through pipelines. The height of an inlet of the hollow container is located between the water draining outlet of the steam pipe and the highest liquid level of the water draining box. According to the water draining device, under the situation that the water draining outlet of the steam pipe is lower than a top connector of the water draining box, an original equipment connector is not changed, a water draining pump, a water draining valve and other equipment are not additionally arranged, and natural water draining is achieved while the steam pipekeeps water seal.