To provide a return filter unit for a hydraulic system which unnecessitates a center shaft and plates of the upper and lower parts and simplifies the constitution.

This return filter unit for the hydraulic system comprises a filter head 21 having an oil inlet 22, a filter case 27 which is disposed on the filter head and has an oil outlet 31 and a filter element 32 which is attachably and detachably disposed inside the filter case. In addition, the filter element 32 is provided with a cylindrical filter member 33 supported by the bottom part 30 of the filter case 27, an element plate 34 having an opening 36 which is disposed on the end part of the filter head 21 side of the filter member 33 and communicates the inside of the filter head 21 with the inside of the filter member 33 and a sealing member 38 which seals fluid-tightly the outer peripheral part of the element plate 34 and the inner peripheral part of the filter head 21.