A liquid filtering instrument 10 according to the present invention achieves filtered liquid by pressure-reduced filtration, and it comprises a filter member 12 in which a liquid filter 15 is accommodated, and a holder member 14 for stocking filtered liquid passed through the liquid filter 15, wherein the filter member 12 and the holder member 14 are formed in capable of being fitted so as to be kept substantially air-tight and water-tight under pressure reduced state.