An image processing device, comprising an image obtaining means that obtains color endoscopic image data, a color space conversion means that converts a color space of the color endoscopic image data to an HSI color space based on hue, saturation and intensity or an HSV color space based hue, saturation and a value, a lesion pixel judgment means that judges, for each of pixels constituting a color endoscopic image, whether or not each pixel is a lesion portion based on the hue and the saturation, a lesion pixel counting means that counts a number of lesion pixels which is a number of pixels judged to be the lesion portion, a lesion index calculation means that calculates a lesion index based on the number of lesion pixels and a lesion index display means that displays the lesion index.
