This experiment was carried out to investigate the effects of proportion of concentrates and roughages on growth and carcass traits of Hanwoo steers. Concentrates and roughages were allotted three levels of 35 to 11%, 44 to 12% and 53 to 13%, respectively from the growing period to finishing period. Concentrate and roughage intake of Hanwoo steers were increased progressively until body weight reached 450kg and 300kg, respectively and reached 1.8 to 1.9% and 1.04 to 1.44% to body weight, respectively but thereafter were decreased gradually. Marbling score and beef grade were tended to be increased when steers were fed 44% roughage compared with the steers fed 35% or 53% at the growing period. Therefore, it can be concluded that feeding 44% of roughage is desirable rather than feeding 35% or 53% of roughage when steers are fattening.