A medical image processing device comprising: an input processing unit (53, 56, 58) for performing an input process of a first color image signal; a color information obtaining section (72, 83, 85, 87) for obtaining two or more pieces of color information from the first color image signal; and a processor for performing an expansion process for changing an angle between a center line and coordinates within a specific angle changing region Rnx containing the center line at an angle change rate Wnx and a compression process for changing an angle between the center line and coordinates within an angle changing region Rny beyond the angle changing region Rnx at an angle change rate Wny in a feature space formed by the two or more pieces of color information, the angle change rate Wny being less than the angle change rate Wnx, wherein the first and second observation areas to be observed are distributed in the feature space, and a distance between the first observation area and the second observation area is D1, and the center line is a first center line provided between the first observation area and the second observation area, and the angle changing region Rnx is an angle changing region R1x containing the first center line, and the angle changing region Rny is an angle changing region R1y beyond the angle changing region R1x, and the angle change rate Wnx is an angle change rate W1x greater than 1, and the angle change rate Wny is an angle change rate W1y less than 1, wherein the feature space is any one of Cb-Cr space formed by chrominance signals Cr and Cb, being the two or more pieces of color information, and ab space formed by color components a* and b*, being the two or more pieces of color information, in a CIE Lab space. an input processing unit (53, 56, 58) for performing an input process of a first color image signal; a color information obtaining section (72, 83, 85, 87) for obtaining two or more pieces of color information from the first color image signal; and a processor for performing an expansion process for changing an angle between a center line and coordinates within a specific angle changing region Rnx containing the center line at an angle change rate Wnx and a compression process for changing an angle between the center line and coordinates within an angle changing region Rny beyond the angle changing region Rnx at an angle change rate Wny in a feature space formed by the two or more pieces of color information, the angle change rate Wny being less than the angle change rate Wnx, wherein the first and second observation areas to be observed are distributed in the feature space, and a distance between the first observation area and the second observation area is D1, and the center line is a first center line provided between the first observation area and the second observation area, and the angle changing region Rnx is an angle changing region R1x containing the first center line, and the angle changing region Rny is an angle changing region R1y beyond the angle changing region R1x, and the angle change rate Wnx is an angle change rate W1x greater than 1, and the angle change rate Wny is an angle change rate W1y less than 1, wherein the feature space is any one of Cb-Cr space formed by chrominance signals Cr and Cb, being the two or more pieces of color information, and ab space formed by color components a* and b*, being the two or more pieces of color information, in a CIE Lab space.