PURPOSE: To achieve a calibration easily and accurately by moving a camera to an arbitrary position to photograph a calibration board which provides a plurality of reference points in a world coordinate system.

CONSTITUTION: A camera 1 is fixed at the tip of an arm 5a, for instance, of a robot 5 so that it can move following the motion of the robot 5. A calibration board 8 is arranged at an arbitrary position in front of the robot 5 to calibrate a camera parameter of the camera 1. A coordinate system on the robot 5 is used to indicate the position and attitude of an object. Moreover, for convenience's sake, a tool coordinate system fixed on the camera 1 and an image plane coordinate system fixed on an image plane of the camera 1 are used. Finally, the camera parameter in the world coordinate system is determined by calibration.