Rearing density is a major factor in welfare production and health of broiler chicks. An experiment was conducted to investigate the effect of rearing density on the behavioral characteristics of Korean native chicks. In the study, 20, 30, and 40 chicks per pen(3.17m2) were used in each treatment and randomly allotted to 6.3bird/m2, 9.5bird/m2, and 12.6bird/m2 density, respectively. The broilers` behavior was recorded for 12 hours continuously during 1 to 8 weeks of age. The time budgets(standing, sitting, and walking) and frequencies of certain behaviors(drinking, feeding, preening, scratching, dust bathing, flapping, aggressive pecking, and pecking) in the broilers were checked during the day. The behavioral characteristics in the early period(1 to 4 weeks) were compared to the later period(5 to 8 weeks) to know the changes in each behavior as the chicks matured. It was observed that 40 chicks per pen showed significant decrease in feed intake and body weight. Corticosterone hormone was higher in the order of 12.6bird/m2 > 9.5bird/m2 > 6.3bird/m2(p<0.05). The behaviors of standing and sitting were the highest in groups of 30 and 40 respectively. The walking behavior was gradually decreased as rearing density increased. The frequencies of the other behaviors also decreased in a high density treatment; especially for feeding, drinking, preening, and pecking. These tendencies widened the gaps of behaviors as time passed. It was concluded that a group of 20 chicks(6.3bird/m2) was the proper rearing density among these three treatments. Broilers in the lower rearing density showed more activity than that with higher density and therefore this environment may lead to better welfare condition.