An output shaft of a power unit having a driven gear for supplying a power of an internal combustion engine via a transmission mechanism and for outputting the power to an outside of a unit case. Borne members are connected respectively at each end of a cylindrical member of the output shaft. The borne members are rotatably supported by the unit case via a pair of bearings. The driven gear is fitted to one of the borne members in a position adjacent to one of the bearings. As a result, the output shaft of the power unit can be manufactured by a compact manufacturing apparatus, and the output shaft can be reduced in weight while maintaining the strength.