At the time of obtaining a difference in intake air amount between right and left banks in a V-type engine, a target value of a lift-amount/operation-angle-varying mechanism provided for each of the banks is set to a target value at which flow velocity of intake air passing through an intake valve becomes almost sound velocity. In a state in which the flow velocity of intake air passing through the intake valve becomes almost sound velocity, a difference in the intake air amount in the right and left banks is detected and, to reduce the difference, a correction value for a target value of a valve lift is set for each of the banks.