Purpose: This study was conducted to investigate factors influencing suicidal ideation in people with mental disorder. Methods: The subjects were 176 people with mental disorder from community mental health centers, social rehabilitation facilities, and university hospital psychiatric outpatient departments. The instruments used included a suicidal ideation questionnaire, a self-esteem scale, a spiritual well-being scale, a family support scale, and a professional support scale. Data were analyzed with t-test, one-way ANOVA, Pearson's correlation coefficient, and hierarchical regression analysis. Results: Suicidal ideation was influenced by age, history of suicidal attempts, and existential spiritual well-being. This study shows that suicidal ideation has negative correlation with existential spiritual well-being, self-esteem, family support, and age. Existential spiritual well-being, history of suicidal attempts, and age accounted for 30% regarding suicidal ideation in people with mental disorder. Conclusion: The lower existential spiritual well-being and age, the higher suicidal ideation. And also suicidal ideation was higher in people who had attempted suicide than in those who had not. Based on the outcomes of this study, it is necessary to design an intervention program that emphasizes existential spiritual well-being in order to decrease suicidal ideation in young people with mental disorder.