Abstract: An image processing device can explicitly distinguish cells to be observed from cells other than those to be observed with a simple configuration. To this end, the image processing device includes a color information obtaining part obtaining at least hue from color information of each pixel of a color image, a detecting part detecting a mode value of the hue on a color space, a range setting part setting a predetermined range on the color space including the mode value of the hue detected by the detecting part as a target range, a changing part changing hue of a pixel included in the target range by virtually performing extension on the target range, and an information converting part converting color information of a pixel having hue not included in the target range into color information indicative of an achromatic color.