1. An estimating polynomial generating device comprising: an analysis data storer storing in advance analysis data comprising input parameter data and corresponding output parameter data; a function surface storer storing in advance an equation for a function surface for limiting the relationship between the input parameter and the output parameter after a homothetic conversion; a homothetic conversion equation storer storing in advance a homothetic conversion equation for performing homothetic conversion of the input parameter and the output parameter; a homothetic conversion parameter searcher searching and establishing factors of the homothetic conversion equation using the analysis data, the equation for the function surface, and the homothetic conversion equation; and an estimating polynomial calculator calculating an estimating polynomial for estimating an output parameter value from an input parameter value by combining the function surface equation and the homothetic conversion equation for which the factors have been established.