The present invention relates to a cookie using the antioxidative activity of purple sweet potato leaf powder and to a manufacturing method thereof. The manufacturing method of the cookie comprises: a first process of putting 28-35 wt% of butter into a vertical electric mixer, stirring the butter smoothly, adding 22-25 wt% of sugar and 0.3-0.8 wt% of salt to the butter, mixing the butter, sugar and salt uniformly, adding 4-7 wt% of egg to the butter, sugar and salt, and mixing the butter, sugar, salt, and egg not to be separated a second process of mixing 1-7 wt% of purple sweet potato leaf powder and 35-43 wt% of wheat flour to form dough, wherein the purple sweet potato leaf powder is obtained by washing and drying leaves separated from purple sweet potato stems, parboiling the leaves in boiling water for 20 seconds, rinsing the leaves in cold water, remove water from the leaves, hot-air drying the leaves at 40°C for 24 hours, grinding the leaves by a food grinder, passing the ground leaves through a sieve of 100 mesh, and keeping the ground leaves frozen at -20°C a third process of molding the dough into a shape of 4×4×14 cm in size, sealing the dough, refrigerating the dough at 4°C for 1 hour, and cutting the dough uniformly into 4×4×0.7 cm in size and a fourth process of putting the cut dough on a flat steel pan, baking the dough in an oven whose temperature is 185°C on the top and 130°C on the bottom for 10 minutes, and cooling the dough at room temperature for 30 minutes. Accordingly, the purple sweet potato leaf powder is used as a food ingredient of bread, a cake, or a cookie in a field of baking, so safe food using environment-friendly food can be offered due to the supply of useful ingredients for the human body, and people&primes health can be protected. Furthermore, the purple sweet potato leaf powder can be used to develop a new health food product according to a consumer&primes pursuit of health and various preferenc
