The living conditions relating to the motor ability of 880 Juveniles of 12∼14 age(447 of urban area, 433 of rural area) are investigated. The relation between the development of motor ability and living conditions is analysed separtely in urban and rural areas. The result of the analysis is as follows : 1. The motor ability is gradually developed with growing age of Juveniles in both areas. However, figure 8 duck in urban area and trunk flexion in rural area show no significant difference with regard to the age of Juveniles. The Juveniles of rural area are superior to the Juveniles of urban area in the motor ability of endurance and balance items. But there is no difference in strength, agility and flexibility items between the two areas. 2. In both areas, the motor ability shows higher relation with health-maturity and exercise state than with other living conditions. The agility item(100m dash) and endurance item(1,000m run) also have higher relations with play and learning state in addition to the above-mentioned living conditions. 3. The period of voice change had a high degree of contribution to all items, except in figure 8 duck in urban area. Exercise favor, unbalanced diet and quentity of meals items also have higher contribution than other living condition items.