Three human cases of tick bite were examined to investigate the occurrence of spotted fever group (SFG) rickettsia in Akita Prefecture. The first case was a 36-year-old male in 1995 with SFG rickettsiosis-like symptoms, such as fever, rash and eschar, who was strongly suspected of being bitten by an adult tick but the tick species was unidentified. Although the etiology remained undetermined at that time, spotted fever group rickettsia infection was definitely diagnosed based on serological diagnosis in 2015. The second case was a 69-year-old female in 2014, and the third one was a 75-year-old female in 2016. They were bitten by a single female tick of Ixodes monospinosus, with Rickettsia helvetica identified genetically. The ticks of both cases were removed early (within 2 days) after tick bite and the patients were administered minocycline prophylactically. They showed no SFG rickettsiosis-like symptoms. Since a patient of SFG rickettsiosis and two R. helvetica-gene positive ticks have been found in Akita Prefecture, the actual situation should be elucidated to take measures in the future.