This observational study was conducted before and after implementing an electronic medical record (EMR) system to evaluate the change in outpatient workflow by implementation of EMR and the effectiveness of clinical documentation improvement (CDI). The number of hours for patient care increased by 89.2% (p < .05) and the hours for writing medical records after consulting decreased after implementation of EMR by 27.3% (p < .01). Implementation of EMR reduced nurses' workload to handle medical records by 78.8 (p < .05) but not changed for physicians. The necessary change in the information management process occurred after using the CDI indicator. We recommend that the “working hours of health professionals” and “handling hours for information resources” should be used widely as CDI indicators to improve workflow when implementing EMR.