To realize the cost reduction of an oil filter by reducing the number of parts.

An element is constituted of a filter medium 5 for filtering oil, a protector 6 for holding the filter medium 5 and the relief valve 7 assembled in the protector 6. The protector 5 is a resin molded article of which the central part is opened in a cylindrical shape and the upper end opening part of the cylindrical opening is formed as an oil escape part 8. The relief valve 7 is constituted of the valve disk 7a for opening and closing the escape port 8 and a leaf spring 7b for urging the valve disk 7a in a valve closing direction. The leaf spring 7b is supported on the upper surface of the annular wall part 6b of the protector 6 at its outer diameter part in the state seated on the seat part 5c of the protector to generate elastic force and the valve disk 7a is pressed to the seat pat 6c by the elastic force. When the pressure on the upstream side of the filter medium 5 becomes higher than the pressure on the downstream side thereof by a predetermined value or more in this releaf valve 7, the valve disk 7a is pushed down against the elastic force of the leaf spring 7b to open the escape port 8.