Method and device for detecting a line-of-sight of a subject and a three-dimensional view-point measurement device. The method uses a first camera, that measures the position of a pupil relative to a coordinate system, a second camera having a light source arranged at a known position in the coordinate system, and forming a corneal reflection center to obtain data of a size of vector r from the corneal reflection center to the pupil center and an angle .phi. of the vector r relative to a coordinate axis of the coordinate system, and a calculation means for calculating a line-of-sight direction based on information from each camera. In determining a relational formula, a subject is made to gaze at a known point to perform measurement and a relational formula is determined. In a line-of-sight determining stage, the subject is measured again using the relational formula. A three-dimensional view-point measurement device can be configured so as to simultaneously measure the lines-of-sights of both eyes with two cameras and two light sources.