To replace an oil filter element without contaminating the periphery.

A cylindrical body 20 is provided in the filter case 2 provided to an oil tank 1 and an oil filter element 5 is inserted in the cylindrical body 20 to be attached thereto. The cylindrical body 20 can be deformed into a first shape wherein an outer cylinder 21 and inner cylinder 22 both of which comprise a flexible material are housed in the filter case 2 in a superposed state and a second shape wherein the inner and outer surfaces of the outer cylinder 21 are reversed and the outer and inner cylinders 21, 22 continue in a longitudinal direction to protrude to the outside of the filter case 2. Since oil does not drip from the outer surface of the cylindrical body 20 when the cylindrical body 20 is set to the second shape to be curved downward to discharge the oil adhering to the inner surface of the cylindrical body 20 to an oil receiver, the oil filter element can be replaced without contaminating the periphery.