Disclosed is an image display device or an image signal output device. The image display device or the image signal output device according to an exemplary embodiment of the present disclosure includes: a receiver for receiving an image; an input unit for receiving a user input to select a display mode or an image signal output mode; a determiner for determining the selected display mode; a depth map generator for generating a depth map for the received image having depth information corresponding to a predefined curvature if the result of determination indicates that the selected display mode is a 3D curved image mode; a 3D image frame generator for generating a left-eye image frame and a right-eye image frame from the received image on the basis of the generated depth map; and an output unit for outputting the generated left-eye image and right-eye image frames.