Objectives This study aimed to propose an efficient mental health service plan to be implemented during epidemics by identifying the mental health characteristics of people who have returned from countries with large-scale coronavirus disease-2019 (COVID-19) outbreaks. Methods We analyzed the mental health evaluation scale data submitted by 504 quarantined people who had returned from countries hit by the COVID-19 pandemic from January to April 2020 through a government support project. Results The average age of the study group was 35.6±8.72 years, and males accounted for 67.1% and females 32.9% of the total subjects. The screening score for post-traumatic stress disorder was met by 12.1% of the subjects. Moderate to high level of depression and anxiety symptoms were seen in 10.7% and 7.0%, respectively. Also, 2.2% of the group complained of clinical level somatization symptoms, and 1.4% were evaluated as being at a high risk of suicide. The average scores and the proportion of subjects at high risk on all scales were significantly higher in female than in male. In a comparison by age, the average score of post-traumatic stress symptoms was significantly higher in subjects in their 20s than those in their 50s, and the proportion of the subjects at high risk for post-traumatic stress symptoms also showed a significant variation between age groups. However, there were no significant differences by age with respect to depression, anxiety, somatic symptoms, and suicidal tendencies. Conclusion During an epidemic, the mental health problems of people may increase, and the risk appears to be higher in female and young adults. Therefore, in addition to strong protection policies, a customized support system for each target group is required.