When a variable valve timing device controls an oil pressure control valve in a manner that a VCT phase is locked at a middle lock phase, an advance chamber and a retard chamber are made to communicate with each other, so that oil is filled into both of the advance chamber and the retard chamber when the oil pressure control valve supplies oil to one of the advance chamber and the retard chamber in an oil filling mode. An oil pump supplies oil to the oil pressure control valve, and is controlled to have an oil flow rate that is equal to or larger than a predetermined value in the oil filling mode.