To provide a method of detecting slurry leakage from filter plates, the anomaly of a filter press, at an early stage, in the filter press including a reciprocating constant discharge pressure pump as a slurry feed pump.

In the anomaly detection method of the filter press having the reciprocating constant discharge pressure pump as the slurry feed pump, the time required for one time slurry feeding immediately after the high pressure feeding of the slurry for each filtering work. When a ratio of T1/T2 of the feeding time T1 immediately after the high pressure feeding in the current filtering work to the feeding time T2 immediately after the high pressure feeding in the previous filtering work is equal to or less than the prescribed value which is less than 1, the slurry is determined to leak from filter plates.