An image analysis system that analyzes an image of an object's organ having an anatomically symmetric shape includes: an image data read means that reads image data of the organ, a memory means that is connected to the image data read means, and stores the read image data, a display means that is connected to the memory means, and displays the image data as an image, a centerline setting means that is connected to the memory means, and sets a centerline of the organ in the image displayed on the display means, a region-of-interest setting means that is connected to the memory means, and uses the centerline to set a plurality of or at least one pair of regions of interest at anatomically symmetric opposite positions in the image of the organ, and an input means that is connected to the region-of-interest setting means, and inputs conditions for setting of the regions of interest in the image.