A factor capable of efficiently regulating expression of an endoplasmic chaperone gene, a nucleic acid encoding it, a complementary strand nucleic acid thereof, a method for regulating expression of an endoplasmic reticulum chaperone gene, and a method for expressing a foreign gene is provided. The endoplasmic reticulum stress transcription factor is capable of regulating transcription-inducing activity, wherein the transcription-inducing activity is exhibited by an element having the nucleotide sequence shown in SEQ ID NO:1 or an element having a nucleotide sequence resulting from substitution of 1 to 3 bases with other bases in the nucleotide sequence as shown in SEQ ID NO:1. A method for controlling expression of an endoplasmic reticulum chaperone, comprising expressing the factor; a method for expressing a foreign protein, comprising positively regulating expression of an endoplasmic reticulum chaperone gene by the method for controlling expression; and a nucleic acid encoding activated form of ATF6, activated form of CREB-RP, suppressive form of ATF6, or suppressive form of CREB-RP, or the complementary strand thereto are also provided. It is expected to be applied to treatment or prophylaxis of cancers, arteriosclerosis, cystic fibrosis, ischemic diseases, wounds or ulcers.