An image distortion correction method is provided which is capable of correcting for distortion of a projected image by designating an arbitrary correction point by using a simple and easy operation without independently providing a display device and/or a pointing device. The distortion correction method includes a first step of displaying first to eighth correction function indicating marks corresponding to first to eighth correction functions to make corrections to first to fourth correction points on a screen, a second step of displaying the first correction function indicating mark corresponding to the first correction function selected by an operator on the screen in a highlighted manner, a third step of moving the first correction point to be corrected by the selected first correction function and to be displayed on the screen according to an instruction of the operator and of calculating a correction parameter corresponding to a moved distance, and a fourth step of correcting for distortion of projected image based on the correction parameter.