1. An optimal solution relation display apparatus, comprising: an objective function approximation unit configured to receive input of a particular number of sample sets, wherein each sample set includes a set of values of a plurality of design parameters and a set of values of a plurality of objective functions calculated in advance corresponding to the values of the plurality of design parameters, and to calculate a plurality of objective function approximating equations by approximating each of the plurality of objective functions by a mathematical equation; an initial optimal design parameter set candidate selection unit configured to select, as candidates for an optimal design parameter set in an initial state, two or more from among sets of the values of the plurality of design parameters included in the sample sets, wherein the two or more correspond to non-dominated solutions in a cost evaluation for a pair of objective functions among the plurality of objective functions; an interpolating design parameter set calculation unit configured to calculate, as one or more interpolating design parameter sets, one or more sets of values of the plurality of design parameters that interpolate between two adjacent components in the candidates; an objective function calculation unit configured to approximate values of the plurality of objective functions using the plurality of objective function approximating equations for each of the calculated one or more interpolating design parameter sets; an optimal interpolating design parameter set selection unit configured to select, as an optimal interpolating design parameter set, an interpolating design parameter set in the calculated one or more interpolating design parameter sets corresponding to a non-dominated solution in the cost evaluation for a pair of objective functions among the plurality of objective functions whose values have been approximated; a process control unit configured to perform integration of the optimal interpolating design parameter set into the candidates to define a result of the integration as new candidates, to determine whether to perform a continuing process or to perform an output process by determining a parameter distance between components in the new candidates, to input the new candidates into the interpolating design parameter set calculation unit and to return control to the interpolating design parameter set calculation unit when the continuing process is determined to perform, and to output the new candidates as final optimal design parameter sets when the output process is determined to perform; and an optimal design parameter set relation information display unit configured to display information relating to the output final optimal design parameter sets.