BACKGROUND: To analyse a medical accident, much time and experience are needed. However, people without experience in analysis have difficulty understanding its conditions and methods, and as a result it takes longer to establish countermeasures. It must be noted that understanding conditions by simply aligning occurrences in the accident in a chronological order is difficult. PURPOSE: A workflow chart that considers time was proposed so that individuals without adequate experience in analysis could easily carry out root cause analysis. METHODS: In the 'workflow chart (WFC)', the time sequence was described horizontally. On the vertical axis, the business manual, the occurrence of the accident, and the time of the occurrence are displayed. In the bottom column of patient event, information regarding damage to patients was written in accordance with time axis. Regarding the degree of damage, the time of error until the accident was identified was connected using a straight line (when the patient was not affected, a dotted line was used) in order to show the overall picture of the accident. RESULTS: According to the time flow chart, hints to identify potential risks were proposed. Focus was placed not only on the error event, but also on keywords such as manual inadequacy, time gap, degree of error and so on to easily lead to the question 'why?' To visualise this, I proposed an operation flow chart. By using time-WFC, even beginners can easily develop accident countermeasure strategies. CONCLUSION: Using a WFC that considers time, time of error and the occurrence of accident could be visualised. As a result, even individuals without experience in analysis could easily perform an analysis.