Wave gear device

This wave gear device is provided with: a noncircular cam which rotates about a vertically extending center axis; a flexible bearing which is mounted on the outer peripheral surface of the noncircular cam and of which the radial length changes in the circumferential direction with rotation of the noncircular cam; a flexible external gear which has a cylindrical shape extending in the axial direction, is mounted at the axially bottom end on the outer peripheral surface of the flexible bearing and which, on the outer peripheral surface of the bottom end, comprises outer teeth provided at a fixed pitch along the circumferential direction; and an internal gear which is arranged radially outside of the flexible external gear, has inner teeth different from the outer teeth, and which meshes partially with the flexible external gear. The inner peripheral surface of the bottom end of the flexible external gear is at least in contact with the outer peripheral surface of the axially upper side of the flexible bearing.