A 40-year-old man developed weakness and myalgia of the shoulders and brachia nine hours after eating a cowfish (Umisuzume, Lactoria diaphana). A clinical symptom showed rhabdomyolysis and serum creatine phosphokinase was elevated to 180,000 IU/L on day 3. Cardiopulmonary arrest and acute renal failure developed after 59 hours and hemodiafiltration was performed. Cerebral death was diagnosed on day 9 and the patient died on day 16. The case has the characteristic clinical course of palytoxin poisoning, which has also been reported as blue humphead parrotfish poisoning from other kinds of fish.