1. A method of spectrum analysis in two-dimensional representation wherein as :for the specific analyzed object, when spectral data where the intensity of the signal output of a spectrophotometer is represented as a function of its wavenumber, wavelength or time are prepared letting n and m (n≠m) be a positive integer, the n-th and m-th derivatives with respect to wavenumber, wavelength or time of intensity on the spectral profile on the said spectral data are calculated, points on the two-dimensional coordinate plane as the X-Y coordinate system whose X-coordinate is the said n-th derivatives and whose Y-coordinate is the said m-th derivatives, respectively, on the said two-dimensional coordinate plane are plotted, and a two-dimensional derivative plot on the said spectral data is prepared, the specific characteristic information on the said spectral data are obtained based on the said two-dimensional derivative plot and wherein based on the said characteristic information, at least one component band is estimated after the band parameter values regarding at least one component band among the component bands contained in the spectral profile of the analyzed object are estimated, the two-dimensional derivative plot with a specific component band removed is obtained by clearing a specific component band or specific component bands already estimated or the two-dimensional derivative plot from the spectral profile or a two-dimensional derivative plot of the analyzed object, specific characteristic information based on the two-dimensional derivative plot with this specific component removed is obtained, band parameter values on remaining component bands are estimated based on the said characteristic information, and the estimation of at least one of the other component bands is iterated, component bands are estimated in order, thereby estimating the component band which comprises a spectral profile of the analyzed object.