Discussed are a stereoscopic image display device to implement high-speed eye-tracking techniques and an eye-tracking method. The stereoscopic image display in one embodiment includes an image panel to alternately display left-eye and right-eye images, a switchable panel disposed at the front or rear side of the image panel to separate the left-eye and the right-eye images from each other to correspond to the left and right eyes of a viewer, a camera mounted to the image panel to capture an image of the viewer, and a computer system to detect position information of the viewer from the image input and calculate midpoint information between the detected position information by interpolation using the detected position information to update position information of the viewer at a faster drive frequency than a drive frequency of the camera, and to control driving of the switchable panel in response to the updated position information.