A 77 years old woman who had a bite with eschar on her left arm, was admitted to emergency ward in our hospital, because of high fever, severe malaise, skin eruption, and consciousness disturbance beginning 5 days previously. She was diagnosed as Japanese spotted fever by seropositive of Rickettsia japonica (R. japonica) antibody, and successfully treated with fluoroquinolone, after minocycline hydrochloride had been proven ineffective. R. japonica-specific DNA was detected by PCR from the tick: Haemaphysalis hystricis larvae collected from a mountainous location in Fukuoka, Japan where the patient had been bitten.