A transmission device capable of transmitting power applied to an input shaft to an output shaft while changing a speed ratio to a plurality of stages, including a single-pinion type first planetary gear mechanism, a single-pinion type second planetary gear mechanism a third planetary gear mechanism; first clutch and second clutches; and first and second brakes. The first planetary gear mechanism is disposed more toward the input shaft side than the second planetary gear mechanism, and the second planetary gear mechanism is disposed more toward the input shaft side than the third planetary gear mechanism, and the first brake is disposed circumferentially outward of the second planetary gear mechanism so as to at least partially overlap with the second planetary gear mechanism, and the second brake is disposed circumferentially outward of the first planetary gear mechanism so as to at least partially overlap with the first planetary gear mechanism.