A vehicule comprising a vehicle power unit, the vehicle power unit comprising: a crankshaft; first and second main shafts (31, 32) disposed in sequence from a side of the crankshaft; a countershaft to be engaged at a time with either the first main shaft or the second main shaft; a crankcase for rotatably supporting the crankshaft, the first and second main shafts (31, 32) and the countershaft such that the crankshaft, the first and second main shafts (31, 32) and the countershaft extend in parallel with each other; first and second clutches (33, 34) disposed on one end portion of a corresponding one of the first and second main shafts (31, 32), the first and second clutches (33, 34) for individually connecting or disconnecting transmission of rotational power from the crankshaft to the corresponding one of the first and second main shafts (31, 32); and gear trains of a plurality of shift speeds (36a, 36c, 36e, 37b, 37d, 37f), each being selectively established through rotation of a shift drum and extending in parallel with each of the first and second main shafts (31, 32) and the countershaft, the power unit changing the shift speeds through exchange of the first and second clutches (33, 34) and transmitting power to a drive wheel from an end portion of the countershaft protruding out of the crankcase, wherein: axial centers (C5, C6) of the shift drum and the countershaft are disposed on different sides of a line connecting axial centers (C3, C4) of the first and second main shafts (31, 32) in a side view as viewed from a direction of an axis of each of the first and second main shafts (31, 32) and the countershaft, characterized in that: in the side view as viewed from the direction of the axis of each of the first and second main shafts (31, 32) and the countershaft, the line is inclined upwardly toward a rear, the axial center of the shift drum is disposed obliquely upwardly toward a front of the line, and the axial center of the countershaft is disposed obliquely downwardly toward the rear of the line, the directions upward, front and rear relating to the top, the front and the rear of the vehicle. a crankshaft; first and second main shafts (31, 32) disposed in sequence from a side of the crankshaft; a countershaft to be engaged at a time with either the first main shaft or the second main shaft; a crankcase for rotatably supporting the crankshaft, the first and second main shafts (31, 32) and the countershaft such that the crankshaft, the first and second main shafts (31, 32) and the countershaft extend in parallel with each other; first and second clutches (33, 34) disposed on one end portion of a corresponding one of the first and second main shafts (31, 32), the first and second clutches (33, 34) for individually connecting or disconnecting transmission of rotational power from the crankshaft to the corresponding one of the first and second main shafts (31, 32); and gear trains of a plurality of shift speeds (36a, 36c, 36e, 37b, 37d, 37f), each being selectively established through rotation of a shift drum and extending in parallel with each of the first and second main shafts (31, 32) and the countershaft, the power unit changing the shift speeds through exchange of the first and second clutches (33, 34) and transmitting power to a drive wheel from an end portion of the countershaft protruding out of the crankcase, wherein: axial centers (C5, C6) of the shift drum and the countershaft are disposed on different sides of a line connecting axial centers (C3, C4) of the first and second main shafts (31, 32) in a side view as viewed from a direction of an axis of each of the first and second main shafts (31, 32) and the countershaft, characterized in that: in the side view as viewed from the direction of the axis of each of the first and second main shafts (31, 32) and the countershaft, the line is inclined upwardly toward a rear, the axial center of the shift drum is disposed obliquely upwardly toward a front of the line, and the axial center of the countershaft is disposed obliquely downwardly toward the rear of the line, the directions upward, front and rear relating to the top, the front and the rear of the vehicle. axial centers (C5, C6) of the shift drum and the countershaft are disposed on different sides of a line connecting axial centers (C3, C4) of the first and second main shafts (31, 32) in a side view as viewed from a direction of an axis of each of the first and second main shafts (31, 32) and the countershaft, characterized in that: in the side view as viewed from the direction of the axis of each of the first and second main shafts (31, 32) and the countershaft, the line is inclined upwardly toward a rear, the axial center of the shift drum is disposed obliquely upwardly toward a front of the line, and the axial center of the countershaft is disposed obliquely downwardly toward the rear of the line, the directions upward, front and rear relating to the top, the front and the rear of the vehicle. in the side view as viewed from the direction of the axis of each of the first and second main shafts (31, 32) and the countershaft, the line is inclined upwardly toward a rear, the axial center of the shift drum is disposed obliquely upwardly toward a front of the line, and the axial center of the countershaft is disposed obliquely downwardly toward the rear of the line, the directions upward, front and rear relating to the top, the front and the rear of the vehicle.