Background: Most antipsychotic drugs studies have been mainly conducted on side effects, randomized clinical trials, utilization rates, and trends. But there have been few studies on the influencing factors in elderly patients. The purpose of this study was to analyze the influencing factors on the outpatient prescription of antipsychotic drugs in the elderly patients. Methods: Active ingredients of antipsychotic drugs in Korea were selected according to the Korean Pharmaceutical Information Center (KPIC)'s classification. Data source was Korean Health Insurance Review and Assessment Service (HIRA) claims data in 2020 and target patient group was the elderly patient group. We extracted patients who have been prescribed one or more antipsychotic drugs and visited only one medical institution. Data were analyzed using descriptive statistics, chi-square, t-test, negative binomial regression. Results: A number of outpatients were 245,197 and prescriptions were 1,379,092. Most characteristics of patients were 75-85 year's old, female, health insurance type, no disease (dementia, schizophrenia), atypical drugs, cci score (>2) and characteristics of medical institution were neurology in specialty, rural region, general hospitals. Results of regression showed that patient's characteristics and medical center characteristics had significant effect on the outpatient prescription of antipsychotic drugs in the elderly patients. Conclusion: This study suggests that national policy of antipsychotic drugs in the elderly patients, with the consideration of the patients' and medical institutions' characteristics, is needed.