In an internal combustion engine, an actuator for driving a control shaft of a variable valve-operating mechanism is disposed in a space surrounded by a cylinder head having a plurality of intake ports, an intake manifold having a plurality of branch pipes connected to the intake ports, and a throttle body disposed at one end in a direction of arrangement of the branch pipes. Thus, the actuator can be disposed by effectively utilizing such an unused space surrounded by the cylinder head, the intake manifold and the throttle body, thereby reducing the entire length and the entire height of the internal combustion engine including the actuator.