A variable valve driving mechanism of an engine includes a rocker arm configured to control open and close of a valve and a servo rocker arm arranged in parallel to the rocker arm. A swing end of the servo rocker arm extends to the top of the swing end of the rocker arm. A valve adjustment gap provided in the swing direction of the servo rocker arm and the rocker arm is formed between the servo rocker arm and the rocker arm. A gap compensating device telescopically filling the valve adjustment gap and configured to adjust the valve to be delayed to close or open in advance when extending to the valve adjustment gap is provided between the servo rocker arm and the rocker arm.