The Min-kia in Yunnan have a legend that their ancestors were Chinese, who migrated from Nanching during the Ming dynasty. This legend has been an obstacle to the understanding of the real origin of the Min-kia. In the present paper the author argues (1) that the legend of their descent from Chinese migrants originated first among the Chinese in Yunnan and then was diffused among the Min-kia, and (2) that even if the Chinese accounted for their own origin by this legend, it would not constitute a consistent hitory, for in the beginning of the Ming dynasty, soldiers from many districts other than Nanching were living in Yunnan. The author is of the opinion that the Min-kia are the surviving descendants of the people who constituted the main portion of the two independent kingdoms, Nanchao and Ta-li in mediaeval Yunnan (s. Vol.14, No.1, p.84). He feels that this people had been assimilated to the Chinese to such an extent that they lost their national pride and accordingly adopted this legend. In his argument, the author compares similar ancestor legends which are found in many parts of China, and asserts the necessity to treat such traditions as legends rather than as historical fact.