We report a case of severe anaphylactic shock in a 5-month-old infant who was scheduled to undergo an external inguinal hernia repair under general anesthesia. Rocuronium used for anesthesia induction was the most likely cause of anaphylaxis. High levels of serum tryptase and histamine detected in the blood sample collected during the anaphylactic reaction confirmed the diagnosis of anaphylactic shock. The patient's clinical status improved within 90 min of intervention by the intravenous injection of vasopressors and a steroid. Surgery was canceled, and the patient stayed in the pediatric intensive care unit (PICU) under artificial ventilation for 5 h before safe extubation. The patient achieved full recovery the next day, without any sequelae. The rescheduled surgery was successfully completed 5 months later under general anesthesia without the use of neuromuscular blocking agents.