To provide the oil coating structure for a gear engagement part capable of surely coating an engagement part of a small-diameter gear hidden in a rear side of a first large-diameter gear with a second large-diameter gear with the lubricating oil.

This oil coating structure for a gear engagement part coats the oil in the gear engagement part provided with the first large-diameter gear 20, the small-diameter gear 21 concentrically provided in a rear side of the first large-diameter gear 20, and the second large-diameter gear 23 to be engaged with the small-diameter gear 21. An oil coating hole 26 facing to the engagement part 25 of the small-diameter gear 21 with the second large-diameter gear 23 is provided in the first large-diameter gear 20.