PURPOSE: To perform solid/liquid separation in a short time and to eliminate contamination of working environment by keeping the concn. of feed liquid to a solid/liquid separator and distribution of particle size of the feed liquid at fixed conditions.

CONSTITUTION: Excess feed liquid 31 received in a feed liquid tank 7 of a solid/ liquid separator is recovered in a storage tank 90 provided with a submarine pump 95, through an overdrain 71 where it is mixed with the feed liquid fed from a feeding port 92 of the feed liquid. Further, the submarine pump 95 sucks the mixed feed liquid 31 from a suction port below the pump, and forces the feed liquid 31 through a feed liquid feeding pipe 33 provided with a flow control valve 97 at the midway of the pipe and scatters the feed liquid again on the surface of a filter medium 1 from an orifice 30 for the waste liquid. A part of the ejected feed liquid discharged by the submarine pump 95 is fed back through a return pipe 96.