A valve train of an internal combustion engine having a swing of a link mechanism that is stabilized to stabilize the operating characteristics of an engine valve. A camshaft is provided together with a valve operating cam pivotally supported by the camshaft so as to operatively open and close an engine valve. A link mechanism allows a drive cam rotated integrally with the camshaft to swing the valve operating cam, and a drive mechanism swings the link mechanism, wherein opening and closing of the engine valve are started in a buffer section of the valve operating cam, and opening/closing timing of the engine valve is controlled by the drive mechanism swinging the valve operating cam via the link mechanism, without the provision of a buffer transition section and a buffer constant-speed section encountered at the time of transiting from a base circle to a cam lobe of the drive cam.