To provide a separating device using gravity difference for removing foreign materials of fine particles contained in a liquid mixture consisting of plural liquids different in gravity being the liquid to be filtrated and separating the liquid mixture into each component and to provide a filter using the separating device.

A partition wall 4 is disposed in a housing 1, which is partitioned into an inflow side region R1 and an outflow side region R2 by a filter member 3, to form in the region R1 a region R4 having the inlet 2a of the liquid L to be filtrated and a housing region R3 for housing a floating liquid (oil component O) by gravity difference in order to separate the region R4 from the region R3.