This study investigated factors affecting the bone mineral density (BMD) of Korean young adult women (20~30 yrs) living in Seoul, according to the state of employment. Data on BMD and anthropometric and biochemical measurements were obtained from the Fifth Korea National Health and Nutrition Examination Survey (KNHANES V) (2010~2011). BMD of the working group (WG) was generally higher than that of the non-working group (NWG). The prevalence of osteopenia, and osteoporosis between the groups was 29.0/31.5%, and 12.9/18.5% from 20~29 yrs as well as 25.5/24.1%, and 20.2/20.5% from 30~39 yrs, respectively. From 20~29 yrs, prevalence of osteopenia and osteoporosis in the WG was lower than that of the NWG. Alkaline phosphatase activity of the WG was lower than that of the NWG. In the WG, from 20~29 yrs, total femur BMD showed significant positive correlations with waist circumstance and BMI. In the NWG, from 20~29 yrs, total femur, femoral neck, and lumbar spine BMDs showed significant positive correlations with weight and fat mass, whereas they showed significant negative correlations with vitamin D. In the WG, from 30~39 yrs, total femur and femoral neck BMDs showed significant positive correlations with weight and free fat mass. The results of this study show that BMD of young adult women is insufficient regardless of their employment status. Therefore, practical and systematic programs are required to improve the BMD of young adult women as well as to maintain healthy bone levels.