Variable valve timing controller for internal combustion engine

A controller for a lock mechanism (90) of an engine valve that readily performs unlocking. A VVT (50) changes the rotational phase of a camshaft (23, 23L, 23R) relative to a pulley (27) in accordance with the difference between the hydraulic pressure of an advance pressure chamber (55) and the hydraulic pressure of a delay pressure chamber (56) to vary the valve timing. The hydraulic pressure difference is set by a variable command value (dvt). A lock mechanism engages a lock pin (92) with a lock hole (96) when the rotational phase of the camshaft matches a lock phase. The VVT enters the most easily unlocking hydraulic pressure state when the command value is set at an unlocking command value (R). An ECU (70) gradually increases the command value from a lower limit value (K- alpha ) to the unlocking command value and then to the upper limit value (K+ beta ) to unlock relative rotation of the camshaft.