The present invention provides a combination of oligonucleotides preferable for composing a rapid and specific gene testing reagent for Shiga toxin family gene type 2 (stx) of entero-hemorrhagic Escherichia coli (EHEC). More specifically, the present invention provides a method for detecting stx2 RNA of EHEC by specifically amplifying only stx2 RNA using a primer having a sequence homologous or complementary to a base sequence specific for stx2 gene of EHEC and located at sites free of alterations between genotypes, and an oligonucleotide that binds to a specific site of stx2 RNA.