PURPOSE: To provide a projection device capable of easily adjusting the magnification of a projected picture.

CONSTITUTION: The projection device is provided with a halogen lamp 1 being a light source illuminating an image, a screen 10 displaying light transmitted through the image, and a projection lens 5 and a motor functioning as the magnification adjusting means adjusting the magnification of the projected image displayed on the screen 10, and also provided with photoelectric conversion element arrays S1 to Sn functioning as a detecting means detecting the end of the projected image displayed on the screen 10 and detecting positional relation between the end of the projected image and the end of a projection area previously set on the screen 10. In accordance with the detected result by the arrays S1 to Sn, the magnification of the projected image is automatically adjusted by the projection lens 5 and the motor so that the entire projected image may be displayed in the projection area.