A 3D image display apparatus includes a light modulator configured to modulate an image light, a difference map generator configured to obtain an absolute value of a difference between a variation value of a left 2D image and a variation value of a right 2D image, an image processor configured to generate 3D image display position information using the absolute value, a light modulator controller configured to partially activate the light modulator in response to the 3D image display position information, an image generator for generating an interlaced image using the left and right 2D images, and an image display device for displaying the interlaced image. The activated area of the light modulator corresponds to an area of the displayed interlaced image, so that the light modulator modulates light provided from the displayed interlaced image, and does not modulate light provided from a remainder of the image.