A 3D display device includes: a data processor configured to generate at least one frame by combining a left-eye image and a right-eye image; a panel including pixels, each of the pixels including three sub pixels; a barrier configured to form a light blocking region and a light transmitting region on the panel on a basis of two sub pixel units; and a controller configured to control the data processor to generate the at least one frame by placing the left-eye image and the right-eye image alternately on the basis of two sub pixels, and to control the panel to display at least one frame generated by the data processor.