An image data analyzing apparatus includes a monocular visual depth information determiner for determining the anteroposterior relationship of regions contained in an image frame of one of a left image and a right image forming stereoscopic image data of time-division display type, a binocular visual depth information determiner for determining the anteroposterior relationship of regions contained in a plurality of images assumed to be the left image and right image, and a left-right image discriminator for outputting left-right image identification information in agreement with an assumption of the binocular visual depth information determiner if a pair of determination results show a high rate of agreement, and outputting left-right image identification information in agreement with a reverse setting of the assumption if the pair of determination results show a low rate of agreement.