PURPOSE: To provide a self-lubricating gear having excellent lubrication performance over a long period by forming a disk-like gear having teeth formed in two lines on its periphery with a deep groove formed between the two lines of teeth, retaining lubricant therein, and closing the opening of the groove by means of an elastic ring.

CONSTITUTION: This gear 20 comprises a disc-like member 22 provided with two lines of teeth 32, 34, and a deep circumferential groove 30 capable of receiving lubricant such as grease is provided between the teeth 32, 34. The groove 30 has a step or shoulder 40 on which an elastic O-ring 42 can be installed, and the O-ring 42 is mounted in the groove 30 to prevent leaking of the lubricant filling the groove 30. The O-ring 42 is sized and positioned so that its top edge 24 projects above the base 44 of the teeth 32, 34, so that when the teeth 36 of a corresponding gear mesh with the teeth 32, 34, a slight pumping action occurs, allowing only a slight amount of lubricant in the groove 30 to flow out.