Atypical hemolytic uremic syndrome (aHUS) is defined by microangiopathic hemolytic anemia, thrombocytopenia, and acute renal failure. The development of aHUS is caused by idiopathic or various secondary potential triggers. The conventional treatment is plasma exchange, but the response and prognosis were poor. Eculizumab, the complement C5 inhibitor, effectively reduced mortality and morbidity. We described a case of aHUS treated with eculizumab. A 35-year-old female patient with no underlying disease underwent dilation and currettage surgery at a local hospital before her visit. She visited our hospital with a sudden lower abdominal pain at postoperative day 1 and was diagnosed with thrombocytopenia, renal failure. Laboratory findings showed that both PT and PTT were identified as normal range. Her platelet counts and renal dysfunction were gradually worsened and schistocytes were identified on the peripheral blood smear test. We performed ADAMTS 13 level and other autoimmune antibody test and performed plasma exchange for exclusion of thrombotic thrombocytopenic purpura. However, there was no effect of plasma exchange. Her platelets dropped to 25 K/mm3 and repeated nasal bleeding with poor hemostasis. We could not perform additional plasma exchange due to high bleeding risk. ADAMTS 13 and autoantibody tests were confirmed to be in the normal range and we were diagnosed with aHUS. She was received eculizumab twice at intervals of a week. Thrombocytopenia and renal dysfunction were rapidly improved after use of eculizumab.