1. An image data analyzing apparatus, comprising: a monocular visual depth information determiner for receiving stereoscopic image data of time-division display type composed of a left image for the left eye of a user and a right image for the right eye of the user, and determining the anteroposterior relationship of regions contained in an image frame of one of the left image and the right image; a binocular visual depth information determiner for receiving the stereoscopic image data of time-division display type, selecting an image assumed to be the left image and an image assumed to be the right image, and determining the anteroposterior relationship of regions contained in an image frame of a plurality of images containing the selected left image and right image; and a left-right image discriminator for receiving a first determination result of the monocular visual depth information determiner, and a second determination result of the binocular visual depth information determiner, comparing the first determination result with the second determination result, determining that an assumption set by the binocular visual depth information determiner is correct if the rate of agreement between the first determination result of the monocular visual depth information determiner and the second determination result of the binocular visual depth information determiner is high, and outputting identification information representing whether each image frame of the stereoscopic image data is the left image or the right image as identification information in agreement with the assumption.