A nationwide questionnaire survey was conducted to clarify the current status of medical experts in mental health evaluation and their needs（recovery rate: 66.6%）. The data were simply tabulated and then statistically analyzed with respect to past experiences of serving as expert witnesses or judges as defined by the Medical Treatment and Supervision Act and past clinical experience. The results showed that 201 respondents（53.0%）had served as medical experts an average of 2.8±2.4 times,while 173 respondents（45.6%）had not served as such experts, and that 284 respondents（74.9%）had served as judges an average of 3.0±2.5 times,while 86 respondents（22.7%）had not served as judges. Although about 70% of the respondents who had served as expert witnesses felt that their experiences were burdensome, mostly due to time-related concerns, most had favorable views of the legal process. More than 70% of the respondents indicated that they would continue to serve as expert witnesses despite their sense of burden, thus suggesting a correlation between a past experience of serving as an expert witness and a willingness to do so again in the future. Furthermore,the results indicate that medical experts in mental health evaluation who have not served as expert witnesses are more hesitant,and since physicians employed at institutions for forensic psychiatric examination are more likely to serve as expert witnesses, a relatively small group of medical experts in mental health evaluation repeatedly serve as expert witnesses. On the other hand, when compared to serving as medical experts, serving as judges was psychologically more stressful for many respondents. Since physicians are not used to being judges, they may experience feelings of resistance or burden. Also, judges are somewhat bound by expert testimony, and the fact that there is no written policy for questioning testimony adds to their stress. Therefore, it will be necessary to clarify the positioning of expert evidence and the decisions made by judges. What medical experts in mental health evaluation needed to improve their knowledge varied depending on the type and duration of work and clinical experience. Therefore, it is necessary to provide information matching the experience,skills,and information related to the practical aspect of the Medical Treatment and Supervision Act. Moreover, the results suggest the necessity for medical experts in mental health evaluation to acquire a wide range of expert knowledge in forensic psychiatry beyond that required for the Medical Treatment and Supervision Act.