Abstract: A filter apparatus for slurries or the like broadly comprises a filter drum housing an accordion-type filter medium, and a cylinder actuator coaxially connected to the filter drum. The accordion filter medium includes a filter screen supported in the form of a bellows between a pair of opposed end plates slidable through the filter drum, one of the end plates being normally held at an open end of the filter drum. The cylinder actuator includes at least one piston rod projecting into the filter drum and connected to the said one end plate by slidably extending through the other end plate. A slurry enters the filter drum through its circumference, passes through the filter screen, and leaves the drum through the one end plate of the filter medium. Sludgy filter cake deposited on the filter screen is compacted and dehydrated as the end plates are moved toward each other by the cylinder actuator, and is removed from the screen as the cylinder actuator further operates to move the filter medium out of the drum.