In this study, two kinds of chestnut-sweet potato (CSP) and pumpkin-sweet potato (PSP) were cooked by three methods: raw, steaming, and roasting. These samples were investigated in food compositions such as moisture, protein, ash, dietary fiber, fat, minerals, and vitamins. As the results of this study, the moisture contents of raw CSP and raw PSP were higher than those of steamed and roasted samples in two cultivars. The contents of protein in raw CSP and raw PSP were 2.57 g/100 g and 3.22 g/100 g, respectively, which were higher than those of other cultivars. The protein contents of roasted CSP and steamed PSP were lower than those of their raw samples. The potassium, phosphorus, magnesium, calcium, sodium, and iron values of PSP were 1,048.46 mg/100g, 152.02 mg/100g, 74.70 mg/100g, 57.22 mg/100g, 22.28 mg/100g, and 1.44 mg/100g, respectively, which were the highest values in tested sweet potato cultivars. The content of dietary fiber in CSP was higher generally than that in PSP. The values of total dietary fiber in cooked sweet potatoes were higher than those of raw sweet potatoes. The contents of vitamins, including thiamine, riboflavin, and niacin, in PSP were higher than those in CSP. Overall, two cultivars of raw, boiled, and roasted sweet potatoes had enhanced food composition. Therefore, these sweet potato cultivars are expected to be highly valuable food items for the development and application of functional foods.