A method for moving viewing positions of a stereoscopic image display system is described. Each cylindrical lens is tilted relative to vertical lines. A data stripe for left eye and a data stripe for right eye making up stereoscopic image data are alternately set to correspond to the cylindrical lenses. At a home position, a long axis of the cylindrical lens agrees with the center of each data stripe, thus concentrating light at a predetermined concentrating position. When setting stereoscopic image data at a different position of sub-pixels that is shifted vertically downward from the home position, the center of the data stripe is shifted relative to the long axis by 0.5 times the length of the sub-pixels horizontally to the left thus concentrating light at a concentrating position moved from the home position in the left-right direction.