Abstract: The present invention utilizes a closed-type vessel comprising a filtering chamber, at least one perforated filter cylinder a portion of which is positioned within the filtering chamber, said filter cylinder being rotatable at any desired speed and having a filtering surface covered with a filter cloth, and a squeezing roll and sealing roll which engage with said filter cylinder through the filter cloth at all times to define a sealing and operating wall. Any sewage to be treated is supplied under pressure to the filtering chamber and filtered through the filter cloth at the filtering surface of the filter cylinder. Filter cake deposited on the filter cloth is continuously transferred to the outer periphery of the squeeze roll and then separated therefrom outside the filtering chamber by any suitable means such as a scraper.