Purpose: The purpose of this study was to identify and analyze the characteristics of nurses’ medication errors during three years. Methods: Retrospective survey study design was used to analyze medication errors by nurses among patient safety accidents. Data were collected for three years from January, 2017 to December, 2019. Data were analyzed using frequency, percentage, x²-test, and logistic regression with SPSS 26.0 program. Results: Of a total 677 medication errors, 40.6% were caused by nurses. Among the medication errors, near miss (n=154, 56.0%), intravenous bolus injection (n=170, 61.8%), wrong dose (n=102, 37.1%) and carelessness for repetitive work (n=98, 35.6%) were the most common. Medication errors differed by department, and nurses’ career, and patient safety accident type. The results of the logistic regression analysis showed that the risk factors of adverse events were medication of fluids (OR=3.93, 95% CI: 1.26~12.27), insulin subcutaneous injection (OR=39.06, 95% CI: 4.58~333.18), and occurrence of extravasation/infiltration (OR=7.26, 95% CI: 1.85~28.53). Conclusion: The simplest and most effective way to prevent medication errors is to keep 5 right, and a differentiated education program according to department and nurse career is needed rather than general education programs. Hospital-level integrated interventions such as a medication barcode system or a team nursing method are also necessary.