Flexible structures with two or more inertia systems connected through spring elements have heretofore presented problems that references and loads do not perfectly accord and that complicated calculations required involve an enormous amount of calculations, a servo control method using feed-forward is characterized by comprising the steps of expressing the position of a load and the position of a motor in respective functions capable of higher order differentiation, determining such functions capable of higher order differentiation from operating conditions (4) and mechanical parameters (5), calculating the motor position, speed and torque reference from the determined functions capable of higher-order differentiation, and using the calculated motor position, speed and torque reference as feed-forward references or of calculating a motor torque reference from the determined function capable of higher order differentiation, inputting the calculated torque reference into a mechanical model, and using the obtained motor position, speed and torque reference as feed-forward references.