The invention provides a lubricating device for a guide rail of an elevator which is adaptable to an oil-retaining member having excellent oil retention with an inexpensive structure, and enhancing the efficiency of the oil feeding work by a worker..A space forming member 5 having a leg part 5a, a supporting plate part 5b for supporting a bottom side of an oil retaining member 3, a cutout part 5cfor allowing an existing supporting member 4 to be inserted therein, and a leaking oil dripping part 5d for allowing leaking oil from the oil retaining member 3 to be dripped on a bottom of a holder member 2, and an oil tank 6 which is integrated with the space forming member 5 to store lubricating oil are incorporated into the existing holder member 2. An oil feed member 7 for feeding lubricating oil from the oil tank 6 to the oil retaining member 3 is provided. The oil retaining member 3 having good oil retention is adaptable to the existing holder member 2, and lubricating oil is successively fed to the oil retaining member 3 from the oil tank 6 stored in the holder member 2 via the oil feed member 7.