The purpose of this study is to investigate the effects of indoor and outdoor exercise environments on bone mineral density and body composition in old women. A total of 26 old women were randomly divided into two groups: an indoor exercise group (IE, n=13) and an outdoor exercise group (OE, n=13). The exercise groups performed moderate exercise (HR max 50~70%; RPE 11-15) three times a week for 60 minutes over 20 weeks. After exercise training, bone mineral density was significantly improved in the OE group as compared with the IE group. Body fat mass was significantly decreased in the IE group. Weight, lean body mass, and body fat mass were significantly decreased in the OE group. Body mass index was significantly decreased in the outdoor exercise group as compared to the IE group. Our findings show that a 20-week program of outdoor exercise training improves bone mineral density and body composition in old women. As mentioned above, it has been found that engaging in an outdoor exercise program for 20 weeks has a positive effect on bone mineral density and body composition in old women. In conclusion, engaging in the outdoor exercise program, including aerobic and resistance exercises, for 20 weeks improved bone mineral density and inhibited bone loss in old women and had a positive influence on vitamin D levels, thereby potentially lowering the risk of osteoporosis.