The ³⁴S/³²S ratios of coexisting sphalerite and galena from Taishu, Toyoha and Kamioka Pb-Zn ore deposits have been measured to estimate the temperature of formation of ore deposit. All of the sphalerite samples were enriched in ³⁴S compared with galena. Sulfur isotopic fractionation between sphalerite and galena ranges from 1.5 2.0 permil in the Taishu and Kamioka deposits, while in the Toyoha deposits ranges mostly from 2.5 to 3.0 permil. The fractionation of coexisting samples from early stage vein in Toyoha deposits is smaller than those from later stage vein. Using these isotopic fractionations and experimental temperature scale (Kiyosu, 1973), the temperature of formation is estimated to be 350° to 400°C in Kamioka deposits, 300° to 350°C in Taishu deposits and 200° to 250° in Toyoha deposits. These isotopic temperatures are slightly higher than filling temperatures determined from fluid inclusions of quartz and sphalerite.