We report the case of a 52-year-old woman, who visited the hospital of Aichi-gakuin University in May, X year, unable to receive dental treatment due to a severe vomiting reaction. Her chief complaint was a dental phobia, which belongs in the category of anxiety disorder. We considered, however, that a conversion mechanism connected to her relationship with her stepmother might also be involved. We undertook not only cognitive-behavioral therapy for the dental phobia but also subjective and supportive psychosomatic treatment for a conversion disorder (hysteria). She was able to go to the dental hospital by herself six months after the first treatment in November, X year, and received treatment for the removal of a tooth stone at the incisor region of the mouth in May, X+1 year. One year after the first treatment, she was also able to receive the same treatment in the molar region of the mouth. We suspect, however, that the vomiting reaction may again prevent her from receiving dental treatment if she needs to spend more time with her stepmother or her own physical condition deteriorates. The psychosomatic treatment for the relationship of the patient with her step mother is being continued and, if necessary, the advice of psychiatrists on liaison shall be sought.