To provide a rotation energizing mechanism effectively easing variations in a rotation speed between an outside member and an inside member, and improving durability.

The rotation energizing mechanism 1 includes the outside member 2 turnable around a first axis X1 and having an annular outside track surface 21 on its inner periphery, the inside member 3 turnable around the first axis X1 and having an annular inside track surface 31 on its outer periphery, and a plurality of balls 4 rollably arranged between the outside track surface 21 and the inside track surface 31. The outside track surface 21 is formed around a second axis X2 inclined to the first axis X1, and the inside track surface 31 is formed around a third axis X3 inclined to the first axis X1. The plurality of the balls 4 are arranged between the outside track surface 21 and the inside track surface 31 to avoid a high load region M where an elastic approach amount is increased most.