[PROBLEMS] To provide a probe useful in the detection of HBV or HBs antigen by which an escape mutant of hepatitis B virus (HBV) possibly occurring in a specimen can be detected; and a method of using the same. [MEANS FOR SOLVING PROBLEMS]A probe capable of recognizing an epitope located on a peptide comprising the amino acid sequence of SEQ ID NO: 1; and a method of detecting hepatitis B virus or hepatitis B virus s antigen by using this probe.
