1. An image processing apparatus comprising: an acquisition means for acquiring image data of a 3D image including a left-eye image and a right-eye image, and superimposed-area information being information on a superimposed area included in the left-eye image and the right-eye image; and a disparity detection means for detecting an amount of disparity in an area excluding the superimposed area identified by the superimposed-area information of the left-eye image and the right-eye image.