Abstract: This invention relates to an apparatus for filtration of lubricating oil which lubricates an internal combustion engine as used in an automobile, a ship, etc. A filter element which is made of filter paper accumulated in layers and a pressure-receiving plate which receives pressure loaded on the lubricating oil during the operation of the internal combustion engine are provided in the filtration apparatus wherein the pressure-receiving plate compresses the filter element in compliance with pressure variations so as to prevent a leak passage from being formed by partial transformation of the filter element.