There are provided first and second extending oil passages supplying operational oil to intake-side and exhaust-side lash adjustors, a first connection oil passage interconnecting one end portions of the oil passages, and an oil-pressure control valve selecting a first state in which the first extending oil passage does not connect to a drain oil passage or a second state in which the first extending oil passage connects to the drain oil passage. An orifice is provided in an oil passage which is located on the side of the first connection oil passage relative to a supply portion of the operational oil supplied to the lash adjustor and located on the side of the first connection oil passage relative to another supply portion of the operational oil supplied to the lash adjustor.