PURPOSE: To broaden a light receiving area on the surface of a CCD, to increase a numerical aperture, to increase the detection probability of a Prukinje image and to improve the sensitivity for infrared region by using a frame transfer type CCD as an area sensor.

CONSTITUTION: A frame transfer type (ET) CCD 10 is used as an area sensor for converting an incident eyeball image to an electric signal. A timing generator 12 transfers the driving timing of the FT type CCD 10 to a CCD driver 11. Also a turning circuit for an infrared light emitting diode lighting circuit (IRED) 13 is made to generate the turning timing of the IRED. The IRED is turned on at the timing of acquisition of the eyeball image data and irradiates the eyeball. The reflected light from the eyeball forms an image on the FT type CCD 10 through a lens. The image data of the eyeball are stored in a memory circuit 16. A calculation circuit 17 for a line of sight calculates the rotation angle of the eyeball based on the stored eyeball image data stored in the memory circuit 16.