To provide a transmission device that has a simple structure, is easily handled and manufactured, and has a wide transmission region and high efficiency.

This transmission device comprises an input shaft 1 and an output shaft 2 rotatably journalled on the same first axis L1. The transmission device also comprises an input crown gear 3 rotating integrally with the input shaft 1 about the first axis L1, an eccentric shaft 4 for transmission externally fitted on the input shaft 1 rotatably about a deviation angular axis P crossing the first axis L1 at a predetermined angle θ, and a crown gear 5 for transmission that is rotatably externally fitted on the eccentric shaft 4, is rotatable about the deviation angular axis P, is revolvable around the first axis L1, and engages with the input crown gear 3. The transmission device also comprises an output eccentric shaft 6 externally fitted on the output shaft 2 side end of the input shaft 1 rotatably about the deviation angular axis P and revolvably around the first axis L1, an output crown gear 7 that is rotatably externally fitted on the output eccentric shaft 6, is rotatable about the deviation angular axis P, is revolvable around the first axis L1, and engages with the crown gear 5 for transmission, and a transmission means Y for rotating the eccentric shaft 4 to change the revolving speed of the crown gear 5. The output shaft 2 is integrally mounted on the output eccentric shaft 6.