A medical image processing device for extracting an endocardium of a left ventricle from 3D image data representing the left ventricle is provided. The device includes: a blood region extracting unit to extract a blood region in the left ventricle from the image data； a convex and concave points identifying unit to find a convex hull from sample points on a contour of the extracted blood region and identify convex points forming the convex hull and concave points, which are sample points other than the convex points； and an endocardium determining unit to deform the contour of the blood region by moving at least a part of the concave points outward from the blood region by an amount determined based on a positional relationship among each concave point and the convex points located around the concave point and determine a deformed contour of the blood region to be the endocardium.
