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 (L2) that passes through an axis of the valve shaft and is perpendicular to a center line (L1) 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 (L1) 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 (L2) that passes through an axis of the valve shaft and is perpendicular to a center line (L1) 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 (L1) 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 (L2) that passes through an axis of the valve shaft and is perpendicular to a center line (L1) 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 (L1) of the throttle body . <EOS>