A projector displays an image on a projection surface. The projector has a zoom adjusting module and a keystone correcting module. The zoom adjusting module adjusts zoom level of a zoom lens for enlarged projection of image light. The keystone correcting module corrects trapezoidal distortion of the image displayed on the projection surface by means of forming the effective panel image in a revised image formation area, the revised image formation area being part of the image formation area of the panel surface.