A first S parameter of a first circuit network including an input port and a connection port is prepared, a second S parameter of a second circuit network is measured, and an overall S parameter of an overall circuit network is calculated. The S parameter of the overall circuit network is calculated as the overall S parameter corresponding to the input port among virtual S parameters of a virtual overall circuit network in which the connection port of the virtual first circuit network is connected with the second circuit network, by using, as an unknown value, a parameter corresponding to the dummy port among virtual T parameters of a virtual first circuit network obtained through conversion of the first circuit network into a symmetric circuit network by adding a dummy port to the input port side of the first circuit network.