We have two myths on first kingdoms of our ancestor’s. One is the Myth of Dankun and the other is the Myth of the Sun-god. The first myth is well-known to us, but the second is little known to us. However many ancient books and monuments have said about our ancestor’s faith in the Sun-god. According to them, kings of Buyeo and Koguryeo, our ancient kingdoms existed in Manchuria and great Amur basin, were believed to be sons of the Sun-god. In present paper, I found many evidences that our ancestors believed in the Sun-god. One of them is the direction of ancient tombs with mural paintings of Koguryeo. These tombs are toward the west, which means that one who visits the tombs has to go toward the east, where the sun rises. Our ancestor’s method to give reverence to the sun is looking toward it. To look toward the east is to believe in the Sun-god. This idea is confirmed by the direction of Buddhist images of Busuk-temple and Sukgulam-temple. They are sitting with face toward the east, the direction of the sunrise. I found that the symbol bird of the sun of our ancestor’s was not a chinese crow with three-legs, but a cock, and that our crow with three-legs is differentiated from Chinese one by comb that our crow has. The comb was originated from comb of cock, our authentic Sun-bird. I found that bird design on clothes of the Gilyak tribe of the Amur, who was believed to be descents of our ancestors, is same as the shape of the bronze incense burner of Bekjae-kingdom. By way of comparing the two, I could explain that the bird on the top of the incense burner is a cock and the small ball under head of the cock is symbol of the sun. I found for the first time in the world the fact that the Koreans went on a great scale over the sea to America in ancient epoch. So I compared our ancestor’s faith in the Sun-god with that of American native’s in order to prove that their faith in the Sun-god were the same as ours. Many features were found in common. One of them is the bird with spread wings, looking toward the sun. Another is number three. The Korean ancestors liked the number three so much that they believed that three was holy number. In the faith in the Sun-god of the aztecs of Mexico and the inkas of Peru was deeply mixed the number three. And the last same feature is the method of giving reverence to the Sun-god, looking toward the sun or the east. In doing research on this theme, I found a very important document saying the content of our ancestors faith in the Sun-god, where appeared three gods, three white birds, three first persons, three suns and our ancestors" legendary tale about the creation of the world.