A gaze direction determination device and a gaze direction determination method that can be determined immediately after the start of measurement without instructing a gaze target and prior adjustment work, and that can determine the gaze direction with high accuracy and accuracy. The line-of-sight determination device (100) includes a line symmetry position determination unit (150) for determining that the left-eye or right-eye cornea reflection image is in a line-symmetric position with respect to the center line of the left and right eye pupils, A line of corneal reflection image including a line-of-sight direction determination unit (170) that determines a line-of-sight direction at a specific position including the installation position of the imaging unit (111) or the irradiation unit (112) at substantially the same position based on the result of the symmetrical position determination. A symmetry is determined, and a specific gaze direction is determined from the line symmetry.注視対象の指示及び事前の調整作業なしに、計測開始直後から判定することができ、高精度かつ正確に視線方向を判定することができる視線方向判定装置及び視線方向判定方法。視線方向判定装置（１００）は、左右の目の瞳孔の中心線に対して、左目又は右目の角膜反射像が線対称の位置にあることを判定する線対称位置判定部（１５０）と、線対称位置判定結果から、撮像部（１１１）又は略同じ位置の照射部（１１２）の設置位置を含む特定位置の視線方向を判定する視線方向判定部（１７０）とを備え、角膜反射像の線対称性を判定し、この線対称性から特定の視線方向を判定する。
