To an internal combustion engine having intake and exhaust valves, there is applied a variable valve timing device. The timing device comprises a first mechanism which varies a working angle of the intake valve within a first given range from a minimum working angle to a maximum working angle; a second mechanism which varies an operation phase of the exhaust valve within a second given range from a most retarded phase to a most advanced phase; and a control unit which controls both the first and second mechanisms in accordance with an operation condition of the engine. The control unit is configured to carry out, when the engine is under an idle operation range, controlling the first mechanism to cause the intake valve to assume the minimum working angle, and controlling the second mechanism to cause the exhaust valve to assume the most advanced phase, and when the intake valve assumes the minimum working angle, controlling the first mechanism to set the open timing of the intake valve to a first point retarded relative to the top dead center (TDC), and when the exhaust valve assumes the most advanced phase, controlling the second mechanism to set the close timing of the exhaust valve to a second point retarded relative to the top dead center (TDC).