[Aim] To shorten required processing time and reduce a memory amount for operations when an area is extracted from an image by using a graph cut method. [Solution Means] An image obtainment unit (10) obtains plural CT images from an X-ray CT apparatus (2), and generates a three-dimensional image (M0). A low-resolution image generation unit (12) performs multi-resolution transformation on the three-dimensional image (M0), and generates a low resolution image (ML). A first extraction unit (14) extracts a specific area, such as the liver region, from the low resolution image (ML) by using a graph cut method. An outline area setting unit (16) sets the outline of the liver region extracted from the low resolution image (ML) in the three-dimensional image (M0), and sets an outline area including the outline in the three-dimensional image (M0). A second extraction unit (18) extracts the outline of the liver region from the outline area, and also extracts the liver region from the three-dimensional image (M0).
