PURPOSE: To execute continuous filtration for a long time without clogging and to improve production efficiency by turning conical rollers in a spiral direction while compressing filter media, and compressing and moving the liquid fed into the filter thereby filtering the liquid.

CONSTITUTION: When a revolving shaft 11 is rotated by driving a motor 13, conical rollers 10, 10 are turned. A pump is then operated to feed forcibly the original liquid to be filtered from a supplying pipe 8 through the opening 7A at the outside end of filter media 7 toward the outermost tube. The original liquid moves toward the inside in the spiral passage while the volume in the arc part partitioned by the rollers 10, 10 is gradually reduced and the amt. corresponding to the reduced volume in the arc part is filtered during said movement. The filtrate is discharged in the form of a clean liquid through an outflow port 6.