A ribozyme comprising the following nucleotide sequence (SEQ ID NO:14) (I): TABLE-US-00001 3'-GUGCCCCA GUACGGUG-5' A C A UGA G AGU N.sup.3 N.sup.1 N.sup.2 wherein A, C, G and U represent a ribonucleotide whose base component is adenine, cytosine, guanine and uracil, respectively, N.sup.1 and N.sup.3 are at least one pair of nucleotides capable of forming a complementary base pair with each other, and N.sup.2 is at least three nucleotides capable of forming a loop.