An internal hub transmission includes a hub axle, a driver rotatably supported by the hub axle, a hub shell rotatably supported by the hub axle, a power transmission mechanism and a shift mechanism. The power transmission mechanism is disposed between the driver and the hub shell for transmitting rotational power from the driver to the hub shell through a plurality of power transmission paths. The power transmission mechanism has at least one planetary gear mechanism that includes a sun gear, a planetary gear and a gear ring. The planetary gear is supported by a gear rack. The planetary gear has helical gear teeth and at least one of the sun gear and the gear ring is provided with helical gear teeth that mesh to helical gear teeth of the planetary gear.