This study was performed in order to compare the changes in fruit quality and antioxidant activity depending on the ripeness degree of the banana flesh and peel (unripe, ripe, and over ripe) when stored at room temperature for 6 days. The moisture contents showed differences such as the significantly lower maturity in the over ripe fruit peel and the moisture content increase in the fruit flesh during ripening. During the maturity stage, the L and b values decreased, while the a value increased. During ripening, the titratable acidity (TA) decreased, while the soluble solids contents (SS), sugar acid ratio (SS/TA), total sugar, and reducing sugar contents increased, respectively. Also during ripening, the glucose and the fructose contents increased considerably, thus resulting in the decrease of the sucrose content. In addition, this study revealed that the phenolic substance, which was part of the fruit skin, showed more favorable reaction to radical ability than the fruit flesh. Furthermore, the DPPH, ABTS radical scavenging ability, and reducing power showed better reaction for the fruit skin than for the fruit flesh, and there was a significant increase in the antioxidative activity as a result of the higher levels of phenolic substance. Therefore, maturity played an important role in changing the chemical composition and physiological activity of a banana. The unripe peels could be used as antioxidant ingredients and they could also enhance the biological activity in the utilization of by-products.