A transmission device for a vehicle, in which check valves are placed in hydraulic pressure supply passages of two systems of a mechanical pump and an electric pump that are driven by a drive source of a travel system, wherein a loss in pressure supplied from a pump is reduced by preventing uneven wear of the check valve. The check valve (70) placed in the hydraulic pressure supply passage from the mechanical pump is disposed between a transmission case (41) and a valve body (40) with a valve case (72) secured to the transmission case and with the direction of the axis of the check valve aligned with the direction of gravity. Oil from the hydraulic pressure supply passage of the transmission case flows in the axial direction, from a valve seat (72a) of the valve case (72) then along recessed grooves (72b), and flows out of outlets (76a, 76c) at the lower end of the valve case into the hydraulic pressure supply passage of the valve body (40). A ball (73) is axially movable between the valve seat (72a) and a stopper part (75a).