An information processing apparatus which carries out stereo matching using stereo moving images obtained by picking up video images of a target simultaneously from different points of view to output position information of the target at a predetermined rate, wherein an image frame pair (61,62) included in the stereo moving images is represented by a plurality of predetermined resolutions (2,4,6,8), the information processing apparatus comprising: a position information production section comprising: a target region determination section arranged to determine, based on a region (68a,68b) including a movement as specified by determining a movement difference for each of the stereo images (61, 62), a target region comprising the region including a movement, the target region to be made a processing target of the stereo matching, a hierarchy determination section arranged to select a resolution to be used in the stereo matching in response to a comparison of the size of the target region at each of the plurality of predetermined resolutions to a reference region size, wherein a resolution is selected in which the target region size is proximate to the size of the reference region, a position specification section arranged to carry out stereo matching using images of the selected resolution, to acquire position information of the target; and a depth image data production section which produces a depth image and updates, based on the acquired position information, the depth image having the selected resolution of the image used for the stereo matching from among a plurality of depth images stored in a memory and representing, by the plurality of resolutions, a depth image representing the position of the target in a depthwise direction as a pixel value on an image plane to output the position information of the target. a position information production section comprising: a target region determination section arranged to determine, based on a region (68a,68b) including a movement as specified by determining a movement difference for each of the stereo images (61, 62), a target region comprising the region including a movement, the target region to be made a processing target of the stereo matching, a hierarchy determination section arranged to select a resolution to be used in the stereo matching in response to a comparison of the size of the target region at each of the plurality of predetermined resolutions to a reference region size, wherein a resolution is selected in which the target region size is proximate to the size of the reference region, a position specification section arranged to carry out stereo matching using images of the selected resolution, to acquire position information of the target; and a depth image data production section which produces a depth image and updates, based on the acquired position information, the depth image having the selected resolution of the image used for the stereo matching from among a plurality of depth images stored in a memory and representing, by the plurality of resolutions, a depth image representing the position of the target in a depthwise direction as a pixel value on an image plane to output the position information of the target.