Caffeine is widely consumed ingredient and it belongs to alkaloids. Many foods that we intake contain caffeine ; coffee, tea cocoa, chocolate, and coke. And it is also added to many commercial remedies ; cold tablets, headache tablets, etc. Effect of caffeine that is known to us so far is as follows; 1. Remaining awake for long hours 2. Increasing concentration and decreasing fatigue 3. Increasing basal metabolic rate 4. decomposing glycogen and body fat and providing energy 5. Stimulating gastric acid 6. Increasing urinary excretion. Caffeine containing beverages(especially, coffee)are also favorite food in adult. In case of children and youth, chocolate and coke are favorite food. So, to intake caffeine containing foods moderately can be a vitality of life. But, a long-term intake or overdose of caffeine can result in many side effects. For example, headache, irritability, restlessness, hypertension, fetal abnormality, etc. Therefore, it is desirable that caffeine intake is under 300-400mg per day. To decrease intake of caffeine, 1. Use decaffeinated coffee 2. Product of decaffeinated coffee bean through gene transformation 3. Indicate content and function of caffeine on caffeine-food container 4. Provide an information of caffeine to public.