To provide a filtration apparatus constituted so as to prevent chattering by automatically compensating abrasion without repairing and replacing an abraded part even if the shaft support part of a screw conveyor is abraded to keep a stable capacity over a long period of time.

The filtration apparatus 1 has a filter tank 2 having a bed comprising a granular filter medium 14 and the screw conveyor 32 vertically arranged in the filter tank 2 to wash a hollow washing tank 38 having an opening 40 provided to the lower end part thereof and the filter medium 14 arranged in the filter tank 2. The screw conveyor 32 is suspended from above in the filter tank 2 and the upper end thereof is driven while the lower end thereof has the shaft 34 supported by the shaft support part 60 fixed to the lower part of the filter tank 2 or the washing tank 38, and the shaft support part 60 has an abrasion compensating mechanism for compensating the abrasion in the contact part of the shaft 34 and the shaft support part 60.