We report a case of Lyme borreliosis (Lyme disease) found in Shizuoka City, Japan which was suspected to be caused by Borrelia japonica infection. A 8-year-old female was bitten on her head by a tick at a camping ground, near Tamagawa, Shizuoka. The tick was removed by the patient and was discarded before species identification. After one week, lymph node swelling with tenderness developed on her left neck. She consulted a local pediatrician and was suspected to have upper respiratory infection. As oral antibiotic, cefaclor was not effective, the patient was referred to us. The patient's serum showed positive reaction with Lyme Borreliosis ELISA kit (Dakopatts, Denmark) using Borrelia burgdorferi flagellum as antigen. The serum also gave positive results with home-made ELISA to B. japonica strain IKA2, which was isolated from I. ovatus, but not with other borrelial strain isolated in the United States, Europe, and from I. persulcatus and wild rodent in Japan. In western blotting, the serum reacted with flagellin and outer surface protein A (OspA) of B. japonica. We diagnosed her as Lyme disease and got a successful result with oral penicillin, sultamicillin. From a result of our field tick survery, we have not collected I. persulcatus around the area where the patient had a tick bite. These findings indicated that Lyme disease was caused by B. japonica infection with I. ovatus bite.