An image for a left eye and an image for a right eye are respectively captured. A corresponding point corresponding to each of a plurality of feature points detected from the image for a left eye is searched for using the image for a right eye. The number of corresponding points found by the search is counted, and it is determined whether to be equal to or more than a predetermined ratio with respect to the number of pixels of the image for a right eye. When the number of corresponding points is determined to be less than the predetermined ratio, the image for a right eye is recaptured, and the corresponding point search process and the determination of whether the number of corresponding points is equal to or more than the predetermined ratio are re-executed using an image new for a right eye obtained by recapture.