An oil strainer in which pressure loss by a turbulent flow in a case (10) is reduced as much as possible. The oil strainer has the case (10) having an inflow opening (112) and an outflow opening (122) that are at positions separated from each other, and also has a filter member (20) provided so as to partition the inner space of the case (10) into a space (SI) on the inflow opening (112) side and a space (SO) on the outflow opening (122) side. A guiding surface (13) is provided in the case (10), and the guiding surface (13) has dam-like ribs (113, 123), extends via a position behind the outflow opening (122) when viewed from the inflow opening (112) side, and converges the flow of oil toward the outflow opening (122).