A rotation urging mechanism includes: an outer member which has an outer raceway surface on its inner periphery and is rotatable about a first axis; an inner member which has on its outer periphery an inner raceway surface disposed in face-to-face relation to a radially inner side of the outer raceway surface over an entire circumference thereof and is rotatable about the first axis; and a plurality of balls disposed rollably between the outer raceway surface and the inner raceway surface. The outer raceway surface is formed about a second axis which is inclined with respect to the first axis, and the inner raceway surface is formed about a third axis which is inclined with respect to the first axis.