A bending meshing type gear device includes a wave generator, an external gear that is bent and deformed by the wave generator, an internal gear that meshes with the external gear, and a wave generator bearing disposed between the wave generator and the external gear, in which an inner ring rolling surface on which a rolling element of the wave generator bearing rolls includes a hardened layer, and the hardened layer has a characteristic that a surface hardness after operating for a predetermined time is increased compared to a surface hardness before operation.