We report a case of endotracheal tube malfunction, in which the inner surface of the tube peeled off during anesthesia. The patient, a 7-year-old boy, was under general anesthesia for the treatment of multiple dental caries. The damaged tube could have caused respiratory failure, putting the patient's life at risk. We speculate that the use of nitrous oxide was one of the contributing factors to the inner wall detachment. Several additional lessons can be learned from this incident in order to prevent tube-related trouble during an operation.