The present invention relates to a stereoscopic image display and a power control method thereof, including a timing controller which varies a driving circuit supply voltage between a first voltage and a third voltage in a 3D mode for displaying a 3D image on a display panel by controlling a power supply circuit and controls the driving circuit supply voltage as a second voltage in a 2D mode for displaying a 2D image on the display panel. The second voltage is lower than the first voltage and is higher than the third voltage.