1. A target mark tracking system for tracking a target mark with a video camera, comprising: a target mark disposed on an object and composed of a black circle and a white triangle centered within said black circle and three-dimensionally shifted from the black circle; a video camera for imaging said target mark; a moving mechanism supporting said video camera and movable in directions with six degrees of freedom; image processing means for processing image data of said target mark from a projected position based on histogram information of said target mark which is produced by said image processing means; and moving mechanism control means for controlling movement of said moving mechanism depending on said shift to enable said video camera to track said target mark; wherein said image processing means processes the image data of said target mark in an image coordinate system to recognize the target mark, store the image data, convert the image data to binary image data, and generate X- and Y-projected histograms.