The invention discloses a filtering device. The filtering device comprises a filtering tank, wherein a tank cover is mounted at the top of the filtering tank; a filtering basket is arranged at the lower part in the filtering tank; the periphery of the upper end of the filtering basket is matched with the inner wall of the filtering tank; annular space is formed between the filtering basket and the filtering tank; an input pipe communicated with the inside of the filtering tank is arranged at the upper part of the side wall of the filtering tank; a cleaning pipe and an output pipe which are communicated with the annular space are arranged at the lower part of the side wall of the filtering tank; a slag discharge port is formed in the bottom of the filtering tank; an open hole connected with the slag discharge port is formed in the bottom of the filtering basket; the outer end of the slag discharge port is connected with a slag discharge pipe. According to the filtering device, solid slag in a liquid can be filtered; by means of the cleaning pipe, the reverse cleaning function of the filtering basket is realized, and the workload of dismounting and washing of a traditional filtering basket through uncovering is reduced; according to the design that the bottom of the filtering basket is open and the solid slag is settled to a slag accumulation tank at any time, the filtering basket has the maximum effective filtering volume all along, and the cleaning period of the filtering basket is greatly prolonged.