A method of designing a control device that controls a controlled variable of a plant to a set point, the control device including a feedback control system for outputting a manipulated variable of the plant based on an output of a feedback controller and a disturbance estimation value, including a step of selecting one of a first order transfer function, a second order transfer function, a third order transfer function, a first order and time delay transfer function, a second order and time delay transfer function, and a third order and time delay transfer function as a transfer function of the nominal plant in accordance with characteristics of the plant; and a step of determining a transfer function of the feedback controller based on a gain and time constant of the nominal plant.