A filtration apparatus includes: a filtration chamber; a sample introducing port for introducing a sample into the filtration chamber; a sample discharge port disposed at a position on an opposite side of the filtration chamber from the sample introducing port; a filtration filter provided in the filtration chamber to filter the sample introduced from the sample introducing port; and a filtrate discharge port for discharging filtrate which has passed through the filtration filter. The filtration filter is disposed such that its filter face is parallel to a flowing direction of the sample introduced from the sample introducing port when the sample discharge port is open. An opening and closing mechanism for opening and closing the sample discharge port is disposed between the filtration chamber and the sample discharge port.