PROBLEM TO BE SOLVED: To provide an estimation device of a visual line direction easing a restriction on a face direction and estimating and tracking with a relatively few cameras, a visual line direction of a measuring object person in real time at any position within an observation area.SOLUTION: A second head position/posture estimation unit 5612 integrates and processes captured image data from a plurality of cameras and executes an estimation process of the position of the head part and the posture of the head part. A center-of-eyeball estimation unit 5614 estimates a three-dimensional position of the center of the eyeball of a specific person subject to the processing, based on a three-dimensional model of the eyeball obtained before an image frame subject to the processing. A center-of-iris extraction unit 5616 detects a projection position of the center of the iris. A visual line direction estimation unit 5618 estimates the visual line direction based on a two-dimensional position in the image frame that is the extracted projection position of the center of the iris and the estimated three-dimensional position of the center of the eyeball.
