We encountered a 12-year-old girl, who had contracted food-borne botulism, and subsequently suffered from obstinate constipation for more than half a year. Even on hospital day 122, Clostridium botulinum and its toxin were detected in her stool specimens. The potency of the toxin of the blood serum sampled before treatment was 20 mouse minimum lethal dose per ml. The toxin in the blood had a molecular size equivalent to that of type A botulinum neurotoxin. On hospital day 250, the patient's serum detoxified type A neurotoxin. We confirmed that the patient had food-borne botulism caused by C. botulinum type Ab, followed by intestinal colonization-type botulism.