Rotation driving mechanism for windmill

A rotation driving mechanism for windmill for use in a windmill including a base-side structure and a rotation-side structure that is rotatable with respect to the base-side structure, so as to rotate the rotation-side structure with respect to the base-side structure, the rotation driving mechanism for windmill comprising:

• an annular track part formed in one structure of the base-side structure and the rotation-side structure, the annular track part having a track wall part whose wall surface is directed toward the other structure of the base-side structure and the rotation-side structure, and first teeth that are arranged such that each facewidth direction thereof radially extends along an in-plane direction of the wall surface;
• a rotation driving part having a rotatable rotating shaft, the rotation driving part being fixed on the other structure;
• and
• a swinging unit including swinging parts each having a meshing part to be meshed with a part of the first teeth, and a swinging part body provided with the meshing part, wherein the swinging parts are arranged along the facewidth direction of the first teeth, and the swinging unit is configured to be relatively moved with respect to the annular track part in a circumferential direction of the annular track part, when the rotating shaft is rotated so that the swinging parts are swung with maintaining a predetermined phase difference thereamong,
• wherein the meshing part includes second teeth to be meshed with the first teeth.