Suicidal ideation increases the risk of suicide. This study investigated the age-specific contributions of sociodemographic factors, health status, and health behaviors to suicidal ideation using nationally representative data. The factors associated with suicidal ideation differ by age. Perceived bad health, stress, and depression had a significant influence on suicidal ideation in all age groups, but their specific effects differed in different age groups. The influence of perceived bad health increased with age, and the effect of stress was strongest among those aged 45-64 years. Moreover, the effect of being depressed decreased by age and was strongest among those 20-44 years of age. Disease and marital status did not have a significant effect on suicidal ideation among those 45-64 years old, and education had no effect among those 65 years or older.