In 1953, when construction of expanding the railroad width of Kokutetsu (Japanese Railway) Nara Line was under way, this pit-type stone room was accidentally discovered, and it revealed 32 Sankakubuchi Shinjukyo Mirrors, the largest number at that time.
1953年（昭和28）、国鉄奈良線の拡幅工事の際に竪穴式石室が偶然発見され、当時最多の三角縁神獣鏡32面が出土した。