A power transmission unit for a vehicle, comprising: a continuously variable transmission that is adapted to alter a speed ratio continuously, and that is disposed between an input shaft to which a torque of a prime mover is inputted and an output shaft that outputs the torque; a first gear train (10, 19) for transmitting the torque when propelling the vehicle in the forward direction; and a second gear train (11, 14, 21, 22) for transmitting the torque to propel the vehicle backwardly by rotating the output shaft in an opposite direction to a rotational direction of the input shaft when propelling the vehicle in the backward direction and that is arranged parallel to the first gear train; a first clutch device configured to selectively allow a torque transmitting route from the input shaft to the output shaft via the first gear train (10, 19) to transmit the torque therethrough; a dog clutch configured to switch the torque transmitting route from the input shaft to the output shaft between a continuously variable speed change route in which the torque is transmitted through the continuously variable transmission and a reverse route in which the torque is transmitted through the second gear train (11, 14, 21, 22); a second clutch device configured to selectively enable and disable both of the continuously variable speed change route and the reverse route to transmit the torque to the input shaft or the output shaft; characterized in that the dog clutch is disposed at a site to transmit the torque from the continuously variable speed change route and the reverse route to the output shaft while switching the torque transmission route between the continuously variable speed change route (12, 27, 28) and the reverse route (11, 21, 22); and in that a drive gear is arranged coaxially with the input shaft so as to commonly serve as one of the gears of a counter gear pair (11, 14) transmitting torque between the input shaft and the continuously variable speed change route (12, 27, 28), and one of the gears of another counter gear pair (11, 21) transmitting torque between the input shaft and the reverse route (11, 21, 22). a continuously variable transmission that is adapted to alter a speed ratio continuously, and that is disposed between an input shaft to which a torque of a prime mover is inputted and an output shaft that outputs the torque; a first gear train (10, 19) for transmitting the torque when propelling the vehicle in the forward direction; and a second gear train (11, 14, 21, 22) for transmitting the torque to propel the vehicle backwardly by rotating the output shaft in an opposite direction to a rotational direction of the input shaft when propelling the vehicle in the backward direction and that is arranged parallel to the first gear train; a first clutch device configured to selectively allow a torque transmitting route from the input shaft to the output shaft via the first gear train (10, 19) to transmit the torque therethrough; a dog clutch configured to switch the torque transmitting route from the input shaft to the output shaft between a continuously variable speed change route in which the torque is transmitted through the continuously variable transmission and a reverse route in which the torque is transmitted through the second gear train (11, 14, 21, 22); a second clutch device configured to selectively enable and disable both of the continuously variable speed change route and the reverse route to transmit the torque to the input shaft or the output shaft; characterized in that the dog clutch is disposed at a site to transmit the torque from the continuously variable speed change route and the reverse route to the output shaft while switching the torque transmission route between the continuously variable speed change route (12, 27, 28) and the reverse route (11, 21, 22); and in that a drive gear is arranged coaxially with the input shaft so as to commonly serve as one of the gears of a counter gear pair (11, 14) transmitting torque between the input shaft and the continuously variable speed change route (12, 27, 28), and one of the gears of another counter gear pair (11, 21) transmitting torque between the input shaft and the reverse route (11, 21, 22).