An apparatus and a method for correcting a distorted image is capable of correcting an optical distortion of an image and misconvergence by prewarping an inputted image without using a convergence yoke, and an image displayer using the same. The apparatus for correcting an image distortion for an image displayer in which an image signal is inputted to display an image on a screen and an image distortion is corrected, includes: a reference image generator for generating a predetermined reference image; a camera for inputting the reference image and photographing an image outputted on the screen; and a distortion information extracting unit for comparing the photographed image outputted from the camera and the reference image outputted from the reference image generator, and generating distortion correction information to correct a distortion of the photographed image in case that the image has been distorted.