An image projection system, an image processing apparatus, and an image processing method are provided, and aim to detect visible and non visible light luminous points on a projection plane image, thus identifying the luminous points are visible light or invisible light; the image projection system comprises an irradiating portion (4) irradiating visible light and invisible light; a projection portion projecting images on the projection plane; a camera portion (10b) taking visible and invisible lights formed on the image of the projection plane in a regulated time; an identifying portion (25) detecting tags corresponding to luminous points of visible and invisible lights in taken image data so as to identify the tags are visible light tags or invisible light tags; synthesis portions (26, 21) combining synthesis information to the image projected on the projection portion according to the positions of the visible light and invisible light tags in the taken image data.