A projector includes a projection section which projects an all-white image and an all-black image onto a screen, a sensor which generates first sensing information by sensing the all-white image and generates second sensing information by sensing the all-black image, a differential image generation section which generates a differential image based on the first and second sensing information, an external light effect removal section, and a projection target area detection section which generates projection target area information on the position of a projection target area corresponding to the screen in the sensing area of the sensor based on the differential image from which the external light effect is removed.