Trisomy 13 is a chromosomal disorder that occurs in complete or partial mosaic forms. It is characterized by central apnea, mental retardation, seizure and congenital heart disease. The survival of the patients with trisomy 13 is the majority dying before one month. Trisomy 13 is the worst life prognosis among all trisomy syndromes. It is reported the cause of death is central apnea. Special needs patients with mental retardation are recognized to have poorer oral health condition. Oral health related quality of life reflects daily activity and well-being. Dental treatment under general anesthesia is sometimes an option for such patients. This patient had received ventricular septal defect closure surgery at 2-year-old. In addition, he had mental retardation and seizure. Dental treatment had been completed without any cerebral and cardiovascular events under non-invasive monitoring with not only cardiac electric velocimetry, but also epileptogenic activity. In addition, postoperative respiratory condition was maintained stable in room air.