PURPOSE: To provide the titled apparatus suitable for the filtration of lubricating oil for an internal combustion engine such as automobile engine, by using a filter element which is compressed according to the pressure variation measured by a pressure-receiving plate, thereby preventing the local crushing of said element.

CONSTITUTION: A filter element 5 consisting of a number of stacked paper sheets and containing the filtrate-discharging apparatus 7 inserted into the hole bored at the center, is placed in the cartridge container 6, which is detachably inserted into the casing 1 of the main body. The stock liquid-introducing pipe 2 is attached to the side wall of the casing, and the filtrate-discharge pipe 3 to the lower wall thereof. The pipe 3 is furnished with the filtrate-discharge path 7, and the pressure-receiving plate 11 to press the element 5 receiving the pressure of the stock liquid is placed on the upper surface of the element 5. An air vent tube 12 is attached to the casing 1 to obtain the objective filtration apparatus.