This study aimed to identify a nutritionally vulnerable group and to examine their nutritional problems based on a relationship between socioeconomic position and nutritional status through life-course. A cross-sectional nationwide survey of 2005 Korean National Health and Nutrition Examination Survey (KNHANES) was used. A total of 8,930 participants aged $geq$ 1 year were included. The socioeconomic position indicator was education level. Nutritional status was assessed by the percentage attainment of a dietary reference intake (DRI) and dietary quality based on nutrient intakes estimated by a 24 hour-recall data. Food insufficiency was examined by one-item food insufficiency questionnaire. The difference in nutritional status and food insufficiency according to educational level was tested by General Linear Model and Chi-square test, respectively. The nutritional status and food insufficiency was the worst during adolescence and older age than other period. Both quantity and quality of nutrient intakes was poorer in low education group than high education group. The prevalence of food insufficiency also was higher in low education group. The results were consistent across the life-course and sex. Based on these findings, we suggest that the development of various policy and strategies targeted to nutritionally vulnerable group is necessary to reduce nutritional inequality by socioeconomic position.