Changes in moisture content and degrees of gelatinization during cooking of sweet potatoes by different cooking methods were studied. The samples were cooked by boiling, steaming, gas oven or microwave oven baking. Changes in the moisture content of sweet potato during cooking were +30.0% by boiling, +4.4% by steaming, -5.8% by gas oven baking, and -46.6% by microwave oven baking. The degrees of gelatinization of sweet potatoes were 83.8%, 75.7%, 73.0% and 67.7%, respectively.