Lead isotope ratios were measured for 54 Han-style bronze mirrors (including 12 mirrors made in ancient Japan) and two bronze arrowheads which were excavated in Japan from the tumuli of the Yayoi and the early Kofun Periods (ca. the 3rd century B.C.-the 4th century A.D.). On the isotope ratio diagram the earlier Han mirrors form a pattern different from most of the mirrors made in later periods in China. From the comparison with Chinese, Korean and Japanese galenas, it was confirmed that the materials of all the objects investigated are of Chinese origin, suggesting that no mines were exploited in Japan before the 4th century A.D. The provenance of the enigmatic triangular-rimmed mirrors is discussed. -- AATA