To provide a transmission device equipped with a hydraulic pressure control mechanism capable of reducing passage resistance at each portion within a hydraulic circuit such as a torque converter, an oil cooler or the like and sufficiently supplying hydraulic oil to a lubrication circuit in the transmission device, in view of problems of the prior art.

The transmission device includes the hydraulic pressure control mechanism having the torque converter 23 disposed on the downstream side of a regulator valve 22 and arranged between a motor and a driving wheel, relief valves 31a, 31b disposed on the upstream and downstream sides of the torque converter 23 so as to control hydraulic pressure supplied to the torque converter 23, and the oil cooler 24 for cooling the hydraulic oil discharged from the torque converter 23. The hydraulic pressure control mechanism supplies the hydraulic oil to the lubrication circuit. The hydraulic control mechanism is provided with a bypass circuit 32 branching off from the regulator valve 22 and bypassing the torque converter 23 and the oil cooler 24 to thereby discharge the hydraulic oil on the downstream side of the oil cooler 24 and supply the hydraulic oil to the lubrication circuit.