Abstract: A checker-arm chain lubricating apparatus is provided that efficiently and surely performs lubrication on a small-size chain and a chain traveling at high speeds. When a checker arm, oscillated by a chain, is returned by the force of a return spring, a cam face of a plunger activating cam fixed to a cam shaft together with the checker-arm operates a plunger of a pump unit via a cam follower to jet lubricant from a lubricating nozzle to the chain. The above-mentioned cam face is formed at a position radially deviated from the center of the cam shaft and the normal direction of the cam face is at generally right angles to the axis of the cam shaft. Consequently, the plunger can be rapidly operated by a small oscillation angle of the checker arm and efficient lubrication in synchronization with chain travel can be performed by a small amount of lubricant jetted from the lubricating nozzle at high speeds.