The purpose of this study is to clarify the influence of non-caffeine green tea and green tea with caffeine on energy substrate during exercise using standard carbohydrate metabolism, fat metabolism, blood free fatty acid concentration and catecholamine. The study subjects were consisted of seven healthy female students and placed into two groups: experimental and control groups. The experimental group was given 336mg of glucose, 336mg of green tea extract, 80 mg of caffeine and 336mg of green tea extract and the control group was given the placebo made of water. Then, both groups exercised for 30 minutes at an intensity of 40% VO2max. Using a bicycle ergometer, the concentration of free fatty acid, adrenaline, and noradrenaline and VO₂, VCO₂, and heart rate were measured. The result showed no significant difference in heart rate between each condition. The noradrenaline concentration after exercise was significantly higher than before and after ingestion in each condition (P.05). Non-caffeine green tea increased noradrenaline concentration after ingestion, and caffeinated green tea significantly increased adrenaline concentration and free fatty acid concentration after ingestion (P.05). In addition, total fat metabolism was significantly higher in caffeine green tea condition than in the control condition (P.05). There was no significant difference in non-caffeine green tea conditions, but the total fat metabolism was higher than the control condition. On the other hand, the total carbohydrate metabolism did not differ significantly from each condition.BR It is suggested that catechin contained in green tea promotes fat burning during exercise and fat food burning effect is increased by additional caffeine intake. This indicates that green tea is effective for obesity prevention for standard weight persons.