A water-stopping structure for a container is disclosed. A float is provided in an internal space of a guiding element. A rod extending from one end of the float is movably received in a tube which penetrates an upper surface of the guiding element. A limiting element in which a water-stopping ball is movably received is mounted around the tube such that the water-stopping ball can be supported by the rod. A lower section of the guiding element is peripherally provided with grooves for guiding water out. A lower cover is mounted around an annular section concavely provided at a lower end of the guiding element. The water-stopping unit thus formed is connected to the bottom of a bucket and placed on a bottom plate so as to stop water from flowing from the bucket to the bottom plate when a predetermined water level is achieved in the bottom plate.