The purpose of this study was to investigate the effect of cooking activities on the unbalanced dietary food habits of elementary school students and develop the effective cooking activity program for the improvement of unbalanced dietary behaviors as well as the food intake and menu acceptance. The subjects of this study were 256 elementary school students. The cooking activity group and control group were consisted of 128 students of $3^{rd}$ & $5^{th}$ grader each. Both cooking activity and the control group took the same 1-hour nutritional theory based class for 10 sessions. Only Cooking activity (CA) group took additional 10 sessions of 1-hour cooking class. Programs for cooking activity were developed and 10 cooking activity sessions were taken place for 4 months. The questionnairs were used to evaluate the effect of the cooking activities over the intake of food group, unbalanced dietary behavior, eating attitudes, menu acceptance before and after the completion of all the cooking activities. Cooking activities affect the unbalanced dietary behaviors and the intake of food groups. Fish, cereals, milk products, fruits, potatoes, vegetables were more eaten by CA group than control group. Eating attitudes and unbalanced dietary behaviors of CA group are also improved significantly than control group. From these results, it was concluded that cooking activities had the positive effect on the improvement of unbalanced dietary food habits over vegetables, cereals, fish, milk product and fruits as well as the unbalanced dietary behaviors of the elementary school children.