Coordination of two actual objects can be checked even if it is difficult to match the objects each other at the same place. An image processing device acquires a projection image that includes an image of a first object projected on a projection surface, and identifies an area, in the projection image projected by projecting means, blocked by a second object in front of the projection surface. The image processing device has projection control means for controlling the projecting means so that a size of the image of the first object projected on the projection surface is life-size, and the projecting means projects the projection image in which a color of the area identified by the object identifying means is replaced by a predetermined color.