The ratio (234)U/(238)U of two groups of ores and the waters collected in Kannokura Deposit was
determined by α-ray spectrometry. According to the geological and mineralogical observation, the ores of each group were formed in succession. Based on the assumption that (234)U/(238)U of the uranium in the leaching solution is higher than that in the ores, the obtained ratio supports the above mechanism of formation. Actually, the waters collected in Kannokura Deposit showed the fairly high value in (234)U/(238)U. Each stratum of a typical section of the mine was observed on the ratio, but the obtained values were in too much complicated relation to interpret.