Using scanning electron microscopy, we investigated how the microstructure of a Cu single crystal with a {15 12 9}aOE (c) 9 10 3 > orientation evolved from cold rolling. The first 50 % rolling caused its crystal orientation to rotate to {211}aOE (c) 111 >. Although orientation splitting occurred near the surface of the single crystal, band-like regions with near-{211}aOE (c) 111 > orientations were still present after the fourth 50 % rolling. We measured the spread of crystal orientation in the near-{211}aOE (c) 111 > regions as a function of the total plastic equivalent strain induced by all rolling steps. When 50 % rolling was performed less than twice, the spread of crystal orientation was proportional to the square root of the plastic equivalent strain. Based on our results, we discussed the relationship between the spread of crystal orientation and the plastic equivalent strain generated by rolling.