A image distortion correction unit which corrects a distortion of a projected image includes: a switching unit which operates in response to an operation signal from a Keystone remote controller button to switch correction by a trapezoidal distortion correction process and correction by a corner distortion correction process back and forth; a determination unit which determines whether any one of the correction by the trapezoidal distortion correction process and the correction by the corner distortion correction process has been performed; and a prohibition unit which prohibits switching the trapezoidal distortion correction process and the corner distortion correction process back and forth if the determination unit determines that any one of the correction by the trapezoidal distortion correction process and the correction by the corner distortion correction process has been performed and the operation signal is also received from the Keystone remote controller button.