The total carotenoid contents in eight sweetpotato (Ipomoea batatas L.) cultivars or breeding lines with yellow flesh were evaluated by absorption spectrophotometry and compared to those of four cultivars with orange flesh. The content ranged from 1.3 mg/100 g dry weight to 3.9 mg/100 g dry weight in yellow-fleshed cultivars and from 13.5 mg/100 g dry weight to 39.9 mg/100 g dry weight in orange-fleshed cultivars. Seventeen carotenoids were detected in yellow- and orange-fleshed sweetpotato by HPLC analysis. The amount of carotenoids analyzed by HPLC correlated highly with the carotenoid content analyzed spectrophotometrically. The main carotenoids were β-carotene 5,8;5′,8′-diepoxide (ca. 32%–51%) and β-cryptoxanthin 5,8-epoxide (ca. 11%–30%) in yellow-fleshed cultivars/lines, while β-carotene (ca. 80%–92%) was dominant in orange-fleshed cultivars. These results suggest that the content of each carotenoid differs according to flesh color, yellow or orange, although the carotenoid component in the yellow and orange flesh was almost identical. The antioxidative activities of carotenoids isolated from yellow-fleshed sweetpotato were analyzed by the 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) radical-scavenging activity. The activity of ipomoeaxanthin A was comparable to β-carotene, and that of β-cryptoxanthin 5,8-epoxide was the lowest. The carotenoids in yellow-fleshed sweetpotato might contribute to the prevention of some diseases due to their antioxidative effect. β-carotene epoxides and β-crypthoxanthin epoxides, which are abundant in the yellow-fleshed cultivars, are noteworthy components for the breeding selection of sweetpotato with deep yellow flesh.