1. A medical image processing device, comprising: a three-dimensional surface shape generation section that generates a three-dimensional surface shape reflecting a surface shape of an observation target in a medical image based on a two-dimensional image obtained from at least one color signal in the medical image including a plurality of color signals; a lesion candidate region detecting section that detects a lesion candidate region which comprises a region with an elevation change or a region with a depression change, utilizing information of the three-dimensional surface shape that is generated by the three-dimensional surface shape generation section; an incidental region detecting section that detects an incidental region that arises because of incidental attributes accompanying a lesion from the medical image; and a detection standard changing section that changes a detection standard when detecting a lesion from the lesion candidate region in accordance with a detection result of the incidental region; wherein the detection standard changing section uses, as the detection standard, a first detection standard when the incidental region is not detected, and a second detection standard which is more relaxed than the first detection standard when the incidental region is detected.