The invention relates to an elution device for treating sludge, which comprises an eluent storage tank, a flocculant storage tank, an elution kettle and a sludge-water separation pool which is arranged under the elution kettle. The elution device is characterized in that the eluent storage tank is connected with the input end of a first channel of a first peristaltic pump by a connection pipe; the sludge-water separation pool is connected with the input end of a second channel of the first peristaltic pump by the connection pipe; the output ends of the first channel and the second channel of the first peristaltic pump are both connected with the upper end of the elution kettle by the connection pipe; the flocculant storage tank is connected with the input end of a second peristaltic pump by the connection pipe; the output end of the second peristaltic pump is connected with the upper end of the elution kettle; the upper end of the elution kettle is provided with an electric motor which is provided with a stirring rod; the bottom of the elution kettle is provided with a sprayer; and the sludge-water separation pool is internally provided with a filtration film. The elution device is a vertical flowing device which can leach and remove heavy metal out of the sludge in batch, recycle an eluent, and enrich and recycle the heavy metal.