A sight line direction estimation device (10) includes: an imaging unit that captures an image of a head portion including an eyeball of a person； an apparent sight line direction derivation unit (102) that derives an apparent sight line direction connecting a center position of the eyeball and an apparent pupil center position on a surface of the eyeball corresponding to a pupil center position based on the image captured by the imaging unit； and a sight line direction estimation unit (108) that estimates an actual sight line direction of the person based on a predetermined corresponding relationship between an actual sight line direction and the apparent sight line direction and the apparent sight line direction derived by the sight line direction derivation unit.
