A stereo image display, switching between a first display direction and a second display direction, includes a polarized light module for providing a polarized light. A first light grating unit is implemented on the light path of the polarized light. When the first light grating unit is activated, the polarized light is modulated to output light in every two column; and when it is turned off, all the polarized light substantially passes. A second grating unit is implemented on the light path of the polarized light. When the second light grating unit is activated, the polarized light is modulated to output light in every two row; and when it is turned off, all the polarized light substantially passes. By the light passing the light grating units, an image displaying unit displays a first image at odd columns or rows and a second image at even columns or rows.