An internal combustion engine comprising: a cylinder body having a cylinder; a cylinder head having an intake port that communicates with the cylinder and connected to the cylinder body; an intake valve supported on the cylinder head for opening/closing the intake port; an intake camshaft supported on the cylinder head and provided with an intake cam for actuating the intake valve; a throttle body connected to the cylinder head and formed with a passage therein; a throttle valve arranged inside the throttle body; a valve shaft provided on the throttle valve and rotatably supported on the throttle body; an actuator for outputting a driving force; a power transmission mechanism having a driving link portion linked to the actuator and a driven link portion linked to the valve shaft for transmitting the driving force of the actuator to the valve shaft; an intake passage including at least the intake port and the passage of the throttle body; and a fuel injector for injecting fuel into the intake passage, wherein the fuel injector has an injection port arranged on a side of the intake valve relative to the valve shaft in a flow direction of an intake air in the intake passage, wherein: as seen along an axial direction of the intake camshaft, the actuator is arranged on a side opposite to the cylinder head with respect to a straight line that passes through an axis of the valve shaft and is perpendicular to a center line of the throttle body, characterized in that as seen along an axial direction of the intake camshaft, the actuator and the fuel injector are arranged on a side of the cylinder head with respect to the center line of the throttle body. a cylinder body having a cylinder; a cylinder head having an intake port that communicates with the cylinder and connected to the cylinder body; an intake valve supported on the cylinder head for opening/closing the intake port; an intake camshaft supported on the cylinder head and provided with an intake cam for actuating the intake valve; a throttle body connected to the cylinder head and formed with a passage therein; a throttle valve arranged inside the throttle body; a valve shaft provided on the throttle valve and rotatably supported on the throttle body; an actuator for outputting a driving force; a power transmission mechanism having a driving link portion linked to the actuator and a driven link portion linked to the valve shaft for transmitting the driving force of the actuator to the valve shaft; an intake passage including at least the intake port and the passage of the throttle body; and a fuel injector for injecting fuel into the intake passage, wherein the fuel injector has an injection port arranged on a side of the intake valve relative to the valve shaft in a flow direction of an intake air in the intake passage, wherein: as seen along an axial direction of the intake camshaft, the actuator is arranged on a side opposite to the cylinder head with respect to a straight line that passes through an axis of the valve shaft and is perpendicular to a center line of the throttle body, characterized in that as seen along an axial direction of the intake camshaft, the actuator and the fuel injector are arranged on a side of the cylinder head with respect to the center line of the throttle body. as seen along an axial direction of the intake camshaft, the actuator is arranged on a side opposite to the cylinder head with respect to a straight line that passes through an axis of the valve shaft and is perpendicular to a center line of the throttle body, characterized in that as seen along an axial direction of the intake camshaft, the actuator and the fuel injector are arranged on a side of the cylinder head with respect to the center line of the throttle body.