A power unit for a vehicle includes a buffering device provided on a final shaft parallel to a countershaft of a speed change gear. The buffering device includes a damper gear wheel supported for relative rotation on the final shaft, a lifter coupled against relative rotation but for relative movement in an axial direction on the final shaft and engaged by a cam provided on one face of the damper gear wheel, a spring retainer supported at a position on the final shaft spaced apart from the lifter, and a coil spring provided between the lifter and the spring retainer for biasing the lifter toward the damper gear wheel. The buffering device is disposed on the final shaft and positioned between a pair of imaginary planes, the pair of imaginary planes extending perpendicularly to an axial line of the idle shaft and passing opposite ends of the idle shaft.