Provided is an image processing apparatus capable of analyzing a target sample image with high accuracy in line with a phenomenon occurring in the target sample. The image processing device includes: a dye spectrum storage portion (233) for storing a dye spectrum of a dye used in staining the stained sample; and an arithmetic portion (250) including: a variation characteristic calculating portion (2501) for calculating, based on the stored dye spectrum, a variation characteristic representing either a sharp or gradual change of the dye spectrum in the wavelength direction; and a dye-amount/variation-amount estimating portion (2503) for estimating, based on the stored dye spectrum and the calculated variation characteristic, a variation amount from a pixel value of each pixel forming the stained sample image based on the dye-amount and the variation characteristic, the arithmetic portion analyzing the stained sample image at least based on the variation amount.