1. An image processing apparatus which generates a first synthetic image and a second synthetic image used for displaying a stereoscopic synthetic image and having disparity with respect to each other, on the basis of a plurality of captured images obtained by capturing with imaging means while moving the imaging means, comprising: a first synthetic image generating means for generating the first synthetic image by synthesizing each of images in a first strip region of the captured images; a second synthetic image generating means for generating the second synthetic image by synthesizing each of images in a second strip region of the captured images which is different from the first strip region; and disparity controlling means for adjusting the disparity of the first synthetic image and the second synthetic image, by shifting at least one of the first synthetic image and the second synthetic image on the basis of a predetermined amount of shift, wherein the disparity controlling means computes a correlation value indicating a degree of correlation between a region in the first synthetic image and a region in the second synthetic image, detects a dominant disparity of the first synthetic image and the second synthetic image by using the correlation value, and computes the amount of shift that cancels out the dominant disparity.