1. A medical image processing device, comprising: an image dividing unit which divides an image corresponding to a subject image which is picked up by a medical image pickup apparatus into a plurality of regions constituted of at least one or more pixels; a feature value calculating unit which calculates a color tone feature value which is a feature value based on a color tone of the image in each of the plurality of regions; a first image region classifying unit which classifies each of regions in which an image of a biological mucosa is picked up as the subject among the plurality of regions as a biological mucosa class; a first color tone reference value calculating unit which calculates a first color tone reference value based on the color tone feature value which each of the plurality of regions has; a first lesion detection reference calculating unit which properly calculates a first lesion detection reference for detecting at least either one of a bleeding site or a redness in accordance with the first color tone reference value; a first image region detecting unit which detects a first target region that is a region in which an image of at least either one of a bleeding site or a redness is picked up among the respective plurality of regions, based on the first lesion detection reference and the color tone feature value which each of the plurality of regions has; a second image region classifying unit which classifies a region in which a yellow color tone is remarkably shown as a yellow mucosal region, among each of the regions classified into the biological mucosa class, based on a classification result of the first image region classifying unit; a second color tone reference value calculating unit which calculates a second color tone reference value based on the color tone feature value which each of the regions classified as the yellow mucosal region has; a second lesion detection reference calculating unit which calculates a second lesion detection reference in each of the regions classified as the yellow mucosal region in accordance with the second color tone reference value; and a second image region detecting unit which detects a second target region which is a region in which an image of at least either one of a bleeding site or a redness is picked up, among each of the regions classified as the yellow mucosal region, based on the second lesion detection reference, and the color tone feature value which each of the regions classified as the yellow mucosal region has.