A valve timing controller includes an electric motor generating a cogging torque on the motor shaft, an current control means for controlling an electricity supplied to the electric motor, and a phase-changing mechanism varying a relative rotational phase between the crankshaft and the camshaft according to a rotation of the motor shaft. The cogging torque has a peak value which is greater than an absolute value of a cam torque applied to the motor shaft from the camshaft through the phase-changing mechanism.