1. A target position identifying apparatus comprising: a color difference converting section for processing pixel values of an image of a target comprised of combination of a first color and a second color obtained from the target under influence of ambient light, thus generating a color component value of the first color, a color component value of the second color and a luminance value; a color region determining section for determining region of the first color and region of the second color, said color region determining section determining the first color region based on whether said first color component value exceeds a threshold value set as a determination condition for each captured image based on either luminance of the captured image or said luminance value, said color region determining section determining the second color region based on whether said second color component value exceeds a threshold value set as a determination condition for each captured image based on either luminance of the captured image or said luminance value; a border detecting section for detecting border between the first color and the second color in the target based on result of the determination by said color region determining section; and a target position calculating section for calculating the position of the target on the image based on result of the border detection by the border detecting section.