1. An image processing device comprising: an adjusting image information storage section adapted to store adjusting images in association with information regarding a direction in which each adjusting image is projected on a projection surface, such that a different adjusting image is stored in association with information regarding a different direction, respectively, the adjusting images being used for adjusting focus of an image to be projected on the projection surface; a detection section adapted to detect information regarding the direction in which the adjusting image is projected on the projection surface; and an adjusting image acquisition section adapted to obtain the adjusting image from among the adjusting images stored in the adjusting image information storage section in accordance with the information regarding the direction detected by the detection section, wherein each of the adjusting images stored in the adjusting image information storage section has a shape of a graphic pattern corrected such that the further a position at which an area of the adjusting image is projected is located from the projector, with respect to the direction in which the adjusting image is projected, the larger a variation in the area of the adjusting image.