The STA gene of Saccharomyces diastaticus encodes the extracellular glucoamylase which hydrolyzes α-1, 4-glucosidic linkage of starch molecule. The expression of STA gene is known to be regulated by STA10 which is a repressor gene in Saccharomyces cerevisiae. To study the regulation mechanism, we constructed various yeast strains containing STA10 or sta10 using both random spore analysis and tetrad analysis. STA10 repressed the STA gene expression at the transcriptional level. We localized UAS (upstream activating sequence) of STA gene by the sequential promoter deletion analysis and constructed the heterologous CYC1::LacZ expression vector of which UAS was substituted with that of STA gene. In yeast strains containing STA10, the UAS of STA gene did not activated the CYC1 promoter. Therefore, the function of STA10 seems to affect the UAS activation of STA gene.