PURPOSE: To enhance a sedimentating effect remarkably by a method wherein a filter is suspended in such a manner as to surround a slurry charging area and to prevent the slurry from flowing, and a solid material adhered to the filter is beaten off by a scraper conveyor.

CONSTITUTION: A grinding oil from a grinding oil pipe 5 is charged in via a charge port 4 of a hopper 3. Although the grinding oil collides against the grinding inside the filter 35 and disturbs the oil surface and the oil therebelow, since the charging area is surrounded by the filter 35, the disturbance is limited to the inside of the filter 35 and it is prevented from propagating throughout the interior of a sedimentation tank 1. When the oil thus charged penetrates through the filter 35, grindings and abrasives contained in the oil are adhered to the filter 35, then sedimentated into sedimentation chambers 37, adhered onto a cover body by a permanent magnet 15 and are scraped away by a scraper 8 of the scraper conveyor 6. On the other hand, the grindings and abrasives adhered to filter 35 are beaten off by the scraper 8 on the return passage side 6b of the scraper conveyor 6, thereby preventing the filter 35 from being clogged.