Both of the house-shaped stone coffins which had been placed as recorded in the Edo period document were covered close to the lid with mud and from their characteristic projects for roping the coffins the front coffin was presumed to be a hollowed-out type and made in the third quarter of the 6th century and the back one in the first quarter of the 7th century.
江戸時代の記録通りに配置されていた家形石棺はどちらも蓋近くまで泥で埋まっており、蓋に付く縄掛け突起の特長から、手前の石棺は刳抜式で6世紀の第3四半世紀に、奥の石棺は7世紀の第1四半世紀にそれぞれ造られたと推定された。