The present invention provides an RNA polymerase III promoter characterized in that a part of its sequence is substituted with a sequence capable of undergoing specific DNA recombination by Cre recombinase in such a manner functions of PSE and a TATA box are not impaired. This RNA polymerase III promoter can be used in a RNAi induction method with the condition that RNAi molecules to be used in analyzing gene function can be induced at an arbitrary point of time or only in a specific tissue (organ).