Natural dyeing of Sangju silk for graveclothes with mulberry extract solution was studied. The anthocyanidin dye in the extracted mulberry solution was markedly influenced by pH condition, which resulted in the changed maximum light absorption from a $lambda$max of 525nm in acidic condition to 380nm in alkaline condition possibly due to the irreversible transformation of anthocyanidin to cyanidin form of the dye. The color fastness properties to both light and washing were good when the fabrics were dyed at $80^{circ}C$ with the mulberry-extracted solution upto twice extraction.