The invention provides a transmission mechanism for use in a vehicle including a vehicle body having one side toward a first direction along the length thereof and the other side toward a second direction opposite to the first direction, the vehicle comprising a differential gear unit 11, an HST 8 and an engine 7 which are arranged in the vehicle body from the first direction side toward the second direction. A transmission 10 is provided between the differential gear unit 11 and the HST 8, whereby the power of the engine 7 is transmitted through the transmission 10 and input to the HST 8 at the first direction side thereof. The transmission mechanism of simple construction serves to shorten the overall length of the vehicle while preventing the rise of the center of gravity of the vehicle.