Catastrophic antiphospholipid syndrome (CAPS) is a lethal disease that occurs suddenly and progresses to multi-organ failure. We present a case of CAPS successfully treated with the rituximab biosimilar CT-P10. A 38-year-old man was referred with a sustained fever and unexplained elevated creatinine levels. Cardiac arrest by ventricular fibrillation occurred upon arrival at the hospital. We diagnosed probable CAPS because of coronary thrombus, renal impairment, suspected diffuse alveolar hemorrhage, and positive anticardiolipin antibody immunoglobulin G. We performed percutaneous coronary intervention for the cardiac arrest, and treated him with extracorporeal membrane oxygenation, mechanical ventilation, and continuous renal replacement therapy. When CAPS was diagnosed, we administered CT-P10 after administering high-dose glucocorticoid. Our case suggests that the use of a rituximab biosimilar is economically efficient in the treatment of CAPS, as in other rheumatic diseases. The patient was cured without recurrence at the 2-year follow-up.