A transmission lubricating structure includes a power transmitting shaft, a main lubricating circuit, and an auxiliary lubricating circuit. The power transmitting shaft includes an ejection hole communicating an inside with an outside of the power transmitting shaft. The main lubricating circuit includes: a main nozzle having a nozzle hole through which lubricating oil supplied from a main tank is discharged to the internal space of the power transmitting shaft; and a hydraulic pump configured to supply the lubricating oil by pressure from the main tank to the main nozzle. The auxiliary lubricating circuit includes an auxiliary nozzle arranged lower than an auxiliary tank and higher than a lubrication target at the outside of the power transmitting shaft, the auxiliary nozzle being configured to drop the lubricating oil, supplied from the auxiliary tank by an own weight of the lubricating oil, toward the lubrication target.