A filtration apparatus for performing solid-liquid separation by immersing a plurality of hollow fiber membranes in a to-be-treated liquid containing a suspended component includes the hollow fiber membranes folded double, a treated liquid collection means communicated with an open end of each of the hollow fiber membranes, a holding member for holding a bent portion of each of the hollow fiber membranes with a gap formed between the bent portion and the holding member, and a gas-jetting means for jetting a cleaning gas from the bent side of each of the hollow fiber membranes to a side of the open end. A gap for flowing the gas jetted by the gas-jetting means is formed between the hollow fiber membranes and the holding member or/and in at least one part of gaps between the hollow fiber membranes.