A motive power transmission device for a vehicle , comprising: a transmission configured to perform gear-shifting and to output motive power input from a drive source ; and a drive shaft that is coupled with the transmission and configured to transmit the motive power from the drive source , which is output from the transmission , to a drive wheel , wherein the transmission has a transmission mechanism unit that is arranged in a transmission casing such that an axis line extends in a vehicle front-rear direction and that performs gear-shifting for the motive power from the drive source , the drive shaft extends in a vehicle width direction on a central side of the transmission mechanism unit in the vehicle front-rear direction and is provided such that the drive shaft passes through the transmission casing , and the transmission mechanism unit includes an input shaft and an output shaft that are arranged on the same axis line, a counter shaft that is arranged in parallel with the input shaft and the output shaft , and a transmission gear unit that has plural gear trains (G1 to G6) each of which is formed with a first gear (31 to 36) provided to the input shaft or the output shaft and a second gear (41 to 46) provided to the counter shaft and meshing with the first gear (31 to 36), characterized in that the transmission mechanism unit further includes a transmission gear operation unit configured to operate the transmission gear unit , the drive shaft extends in the vehicle width direction through a portion between the transmission gear unit and the transmission gear operation unit , the drive shaft extends in the vehicle width direction through a portion between the transmission gear unit and plural shift rods of the transmission gear operation unit , and the plural shift rods are arranged to extend in the vehicle front-rear direction above the drive shaft . a transmission configured to perform gear-shifting and to output motive power input from a drive source ; and a drive shaft that is coupled with the transmission and configured to transmit the motive power from the drive source , which is output from the transmission , to a drive wheel , wherein the transmission has a transmission mechanism unit that is arranged in a transmission casing such that an axis line extends in a vehicle front-rear direction and that performs gear-shifting for the motive power from the drive source , the drive shaft extends in a vehicle width direction on a central side of the transmission mechanism unit in the vehicle front-rear direction and is provided such that the drive shaft passes through the transmission casing , and the transmission mechanism unit includes an input shaft and an output shaft that are arranged on the same axis line, a counter shaft that is arranged in parallel with the input shaft and the output shaft , and a transmission gear unit that has plural gear trains (G1 to G6) each of which is formed with a first gear (31 to 36) provided to the input shaft or the output shaft and a second gear (41 to 46) provided to the counter shaft and meshing with the first gear (31 to 36), characterized in that the transmission mechanism unit further includes a transmission gear operation unit configured to operate the transmission gear unit , the drive shaft extends in the vehicle width direction through a portion between the transmission gear unit and the transmission gear operation unit , the drive shaft extends in the vehicle width direction through a portion between the transmission gear unit and plural shift rods of the transmission gear operation unit , and the plural shift rods are arranged to extend in the vehicle front-rear direction above the drive shaft . <EOS>