A structure wherein a shift actuator is disposed in a power unit for a saddle-ride type vehicle, the structure comprising: an engine with an engine main body; a crankcase forming a part of the engine main body; a crankshaft rotatably supported by the crankcase; a transmission mechanism disposed in the course of power transmission from the crankshaft to a drive wheel and installed in the crankcase; a shift actuator which drives and controls the gear-shifting action of the transmission mechanism and which is disposed in the engine main body, the shift actuator being attached to a side surface of the crankcase with the operational axis of the shift actuator being placed in a plane that is orthogonal to the axial direction of the transmission mechanism, characterized in that the engine further comprises a valve-operating device provided additionally with valve operation mode change mechanisms (63, 64) capable of changing operation modes of engine valves (44, 45), a clutch device for switching the making/breaking of power transmission between said crankshaft and the transmission mechanism, said clutch device disposed on a lateral side of said crankcase on the side of one end of said crankshaft, a valve operation controller for controlling,the operations of said valve operation mode change mechanisms (63, 64), and a speed change controller for controlling a gear change operation of said transmission mechanism, said valve operation controller and said speed change controller being attached to the engine body inclusive of said crankcase, wherein said valve operation controller and said speed change controller are attached to said engine body on the opposite side of said clutch device with respect to a vehicle body center line in a direction along the axis of said crankshaft. an engine with an engine main body; a crankcase forming a part of the engine main body; a crankshaft rotatably supported by the crankcase; a transmission mechanism disposed in the course of power transmission from the crankshaft to a drive wheel and installed in the crankcase; a shift actuator which drives and controls the gear-shifting action of the transmission mechanism and which is disposed in the engine main body, the shift actuator being attached to a side surface of the crankcase with the operational axis of the shift actuator being placed in a plane that is orthogonal to the axial direction of the transmission mechanism, characterized in that the engine further comprises a valve-operating device provided additionally with valve operation mode change mechanisms (63, 64) capable of changing operation modes of engine valves (44, 45), a clutch device for switching the making/breaking of power transmission between said crankshaft and the transmission mechanism, said clutch device disposed on a lateral side of said crankcase on the side of one end of said crankshaft, a valve operation controller for controlling,the operations of said valve operation mode change mechanisms (63, 64), and a speed change controller for controlling a gear change operation of said transmission mechanism, said valve operation controller and said speed change controller being attached to the engine body inclusive of said crankcase, wherein said valve operation controller and said speed change controller are attached to said engine body on the opposite side of said clutch device with respect to a vehicle body center line in a direction along the axis of said crankshaft.