Abstract: An oil filter is provided comprising a bottomed cylindrical casing (8, 106, 208), a base member including an oil inlet port (91c) and an oil exit port (91b) and adapted to close an open end of the casing and an isolating means (6, 107, 115, 206) formed about the filter element for isolating first and second oil paths to communicate one end and the periphery of a filter element formed by wrapping many times a sheet of thin filter paper about a core member with the first oil path (A) communicated with an oil inlet port and to communicate the other end of the filter element to the second element (B).With this construction, since the first oil path communicated with the oil inlet side is positioned close to the end surface and the periphery of the filter element, the area upon which the oil collides and severe clogging is liable to occur can be increased thus maintaining the filtering capability over a long period.