A control system that constantly and accurately controls a control variable so that it remains within an allowable range is provided. The control system in accordance with the present invention estimates a steady-state deviation d in a controlled object as a steady-state deviation estimation value d on the basis of a control variable y and a final desired value y₂. A control variable y in a controlled object based on the initial desired value y₁ is estimated as the primary estimation value y₁ on the basis of at least the initial desired value y₁ and the steady-state deviation estimation value d. If a primary estimation value y₁ is within an allowable range, then a final desired value y₂ agreeing with an initial desired value y₁ is determined, while, if the primary estimation value y₁ is out of the allowable range, then the final desired value y₂ is determined on the basis of at least a boundary value of the allowable range. A manipulation variable x is determined on the basis of the final desired value y₂.