The method of the harmonic analysis of the human operator's characteristics by means of an analog computer is described. The human operator's characteristics in the closed loop system are described by vector locus. The human operator controls in response to the sine wave input so as to make constant the gain in the closed loop system. In accordance with the change of the input frequency, the operator changes his control action. Consequently the transfer function of the human operator's characteristics is too complex and difficult to be described by a linear element.