The Naga-une mounded tomb No.10 is supposed to be a round or scallop shell-shaped mounded tomb located in Mirasaka-chō, Miyoshi City, Hiroshima Prefecture. As part of “Field Practice in Archaeology C” for the twenty-fifth annual class of archaeology majors at the Hiroshima University School of Letters, we conducted a topographic survey of this mound with the aim of clarifying its scale, shape and the date of its construction. This mounded tomb has been altered by land reclamation for a vineyard, however, we could reconstruct its shape according to the plan, based on some parts that so far remained in good condition. The results of this survey indicated that the Naga-une mounded tomb is a scallop shell-shaped mounded tomb of the Kofun period, 19.5m in length and was constructed in the second half of the 6th century AD (additional interment may be performed at the beginning of the 7th century). This allows the conclusion that the building of small scallop shell-shaped mounded tombs also continued in the second half of the Late Kofun period. Additionally, we assumed the possibility that this mound has a corridor-style stone chamber with horizontal side entrance because of the additional interment, and that many kinds of the Sue ware were put on the floor of this chamber, which was typical in the regions of Miyoshi and Shōbara City in the northern part of Hiroshima Prefecture and the San’in region.