PROBLEM TO BE SOLVED: To provide a planetary gear mechanism which achieves reduction of manufacturing costs and can efficiently supply an oil to an oil passage in a pinion shaft.SOLUTION: A first member 10 includes: a first joint part 11 joined to an outer peripheral surface of a flange part 92; and a first shaft support part 12 which supports a pinion shaft 30 at one side in an axial direction L with respect to a pinon gear 5. The second member 20 includes: a second joint part 21 joined to the first member 10; and a second shaft support part 22 which supports the pinion shaft 30 at the other side in the axial direction L with respect to the pinion gear 5. A first oil passage 41 which is formed in the flange part 92 and extends in a radial direction R and a second oil passage 42 formed in the pinion shaft 30 communicate through a third oil passage 43 formed in an interior part of the first member 10. The first oil passage 41 and the third oil passage 43 are connected on a joint surface between the outer peripheral surface of the flange part 92 and the first joint part 11.SELECTED DRAWING: Figure 1
