FILTRATION APPARATUS

A filtration apparatus in which hollow fibers are immersed in a raw liqui d to be treated which contains a suspended ingredient to cause the raw liqui d to undergo solid/liquid separation and a treated liquid to permeate. It co mprises: the hollow fibers which have been folded in two; a treated-liquid c ollection means communicatively connected to the open ends of the hollow fib ers; a holding member which holds the folded parts on the other end side of the hollow fibers while leaving a space; and a gas ejection means for ejecti ng a cleaning gas toward the open ends from the other end side of the hollow fibers. The hollow fibers held by the holding member are at least partly sp aced from the holding member and/or the hollow fibers are at least partly sp aced from one another to thereby form spaces for passing the gas to be eject ed from the gas ejection means.