An image display apparatus detects a projection angle of a projection unit that projects a screen image on a screen and is capable of vertically changing the projection angle, and corrects trapezoidal distortion of the screen image according to the projection angle. The image display apparatus changes the amount and direction of trapezoidal distortion correction based on the projection angle. The image display apparatus also determines whether a projection mode is projection upward to a wall or projection to a ceiling and changes the direction of trapezoidal distortion correction for projection upward to the wall and projection to the ceiling. Specifically, for projection upward to the wall, a correction factor is positive and an upper edge portion of the screen image is compressed for correction; and for projection to the ceiling, a correction factor is negative and a lower edge portion of the screen image is compressed for correction.