1. A cardiovascular OCT image making method which reduces artifacts comprising steps of: inputting a cardiovascular OCT image; converting coordinates of the inputted OCT image into two-dimensional polar coordinates (θ and r); generating a brightness control function of an A-line direction based on a blood wall relative to each θ value; forming a brightness image in the A-line direction based on the blood wall and depending on the brightness control function; and forming an OCT image of which brightness is controlled by the brightness image by applying the brightness image formed on the inputted OCT image.