A stereoscopic image display apparatus comprising: a one-side electrode (310, 320) comprising a plurality of extension electrodes (313, 323) spaced apart from each other including first one-side extension electrodes and second one-side extension electrodes; an opposite-side electrode (510, 520) comprising a plurality of extension electrodes (513, 523) spaced apart from each other including first opposite-side extension electrodes and second opposite-side extension electrodes; and a liquid crystal unit interposed between the one-side electrode and the opposite-side electrode for forming barrier patterns based on an electric field or potential difference selectively formed therebetween, wherein one of the extension electrodes (313, 323) of the one-side electrode overlaps at least two of the extension electrodes (513, 523) of the opposite-side electrode, and wherein a state in which the barrier patterns formed in the liquid crystal unit are arranged is changed based on voltages or pulses applied to the one-side electrode and the opposite-side electrode in response to a change in position of eyes or a head of a user, wherein each of the extension electrodes of the one-side electrode has a first width and each of the extension electrodes of the opposite-side electrode has a second width, wherein the first width is greater than the second width, wherein opposite electric potentials are applied to the first one-side extension electrodes and the second one-side extension electrodes as driving signals for controlling the barrier patterns in the form of pulse sequences (C1, C2), which for each of the one-side extension electrodes (313, 323) remain unchanged regardless of the change of the barrier patterns, and wherein different electric potentials are applied to the first opposite-side extension electrodes and the second opposite-side extension electrodes in the form further pulse sequences (S1, S2), which for each of the opposite-side extension electrodes (513, 523) are changed according to the change of the barrier patterns. a one-side electrode (310, 320) comprising a plurality of extension electrodes (313, 323) spaced apart from each other including first one-side extension electrodes and second one-side extension electrodes; an opposite-side electrode (510, 520) comprising a plurality of extension electrodes (513, 523) spaced apart from each other including first opposite-side extension electrodes and second opposite-side extension electrodes; and a liquid crystal unit interposed between the one-side electrode and the opposite-side electrode for forming barrier patterns based on an electric field or potential difference selectively formed therebetween, wherein one of the extension electrodes (313, 323) of the one-side electrode overlaps at least two of the extension electrodes (513, 523) of the opposite-side electrode, and wherein a state in which the barrier patterns formed in the liquid crystal unit are arranged is changed based on voltages or pulses applied to the one-side electrode and the opposite-side electrode in response to a change in position of eyes or a head of a user, wherein each of the extension electrodes of the one-side electrode has a first width and each of the extension electrodes of the opposite-side electrode has a second width, wherein the first width is greater than the second width, wherein opposite electric potentials are applied to the first one-side extension electrodes and the second one-side extension electrodes as driving signals for controlling the barrier patterns in the form of pulse sequences (C1, C2), which for each of the one-side extension electrodes (313, 323) remain unchanged regardless of the change of the barrier patterns, and wherein different electric potentials are applied to the first opposite-side extension electrodes and the second opposite-side extension electrodes in the form further pulse sequences (S1, S2), which for each of the opposite-side extension electrodes (513, 523) are changed according to the change of the barrier patterns.