A valve timing control device includes: a unit for calculating a target
valve timing for one of an intake valve and an exhaust valve in
accordance with an operational state; a unit for detecting an actual
valve timing of one of the intake valve and the exhaust valve; an actual
valve timing control unit for generating a controlled variable for the
VVT based on a difference between the target valve timing and the actual
valve timing; a unit for learning a learning value of the controlled
variable required for maintenance of the actual valve timing based on an
integral correction value; and a unit for detecting a malfunction in a
VVT from an amount of a shift in the actual valve timing when learning is
not completed yet, and for detecting a malfunction in the VVT from the
difference when learning is already completed.