Provided are an image processing device, etc. that, even when two or more tissues are present in a subject, can accurately estimate the depth at which a specific tissue is present. An image processing device 100 that, on the basis of an image captured of a subject using light of a plurality of wavelengths, estimates the depth of a specific tissue contained in the subject, the image processing device being provided with: an absorbance calculating unit 141 that, from the pixel value of each of a plurality of pixels that constitute the image, calculates absorbance at the plurality of wavelengths a component-quantity estimating unit 142 that, from the absorbance at the plurality of wavelengths calculated by the absorbance calculating unit 141, uses the absorbance at a first wavelength band, which is one portion of the plurality of wavelengths, to estimate a component quantity for two or more absorbance components that are included in each of two or more tissues that include the specific tissue an estimation-error calculating unit 143 that calculates the estimation error of the component-quantity estimating unit 142 and a depth estimating unit 145 that estimates the depth at which the specific tissue is present in the subject on the basis of the estimation error for a second wavelength band that has shorter wavelengths than the first wavelength band.La présente invention concerne un dispositif de traitement dimage, etc. qui, même lorsque deux tissus ou davantage sont présents chez un sujet, permet destimer avec précision la profondeur à laquelle un tissu spécifique est présent. Linvention porte plus précisément sur un dispositif de traitement dimage (100) qui, sur la base dune image capturée dun sujet au moyen de la lumière dune pluralité de longueurs donde, estime la profondeur dun tissu spécifique contenue dans le sujet, le dispositif de traitement dimage étant pourvu des éléments suivants : une unité de calcul dabsorbance (141) qui, à partir de la valeur de pixel de c
