1. An image processing apparatus for processing a stained sample image obtained by imaging a stained sample, the image processing device comprising: a dye spectrum storage portion for storing a dye spectrum of a dye used in staining the stained sample; and an arithmetic portion including a variation characteristic calculating portion and a dye-amount/variation-amount estimating portion, the variation characteristic calculating portion calculating a variation characteristic based on the dye spectrum stored in the dye spectrum storage portion, the variation characteristic representing either a sharp or gradual change of the dye spectrum in the wavelength direction, the dye-amount/variation-amount estimating portion estimating, based on the dye spectrum stored in the dye spectrum storage portion and the variation characteristic calculated by the variation characteristic calculating portion, a dye-amount and a variation amount based on the variation characteristic from a pixel value of each pixel forming the stained sample image, the arithmetic portion analyzing the stained sample image at least based on the variation amount.