If a projection display device includes a shifting mechanism for shifting a projection lens to adjust the direction in which the display projects an optical image, it is difficult to find suitable position where the display should be installed. Thus, the projection lens is fitted with a projection angle adjusting mechanism, which includes an adjusting dial having a scale representing the position of the lens relative to a display element. The projection display device is capable of automatically displaying on the projected optical image a scale image corresponding to the scale. The projection display also is capable of displaying on the projected optical image the position of the optical axis of the projection lens, which can be shifted by the adjusting mechanism.