Railway track irregularities need to be kept at a satisfactory level through appropriate maintenance work by using MTTs (Multiple Tie Tamper). We have developed an optimal track maintenance scheduling model taking train derailment accident risk into consideration. Firstly, we analyze derailment accident data in order to build a model for estimating the number of casualties when a train derailment accident occurs. Next, by applying the result, we develop an optimal track maintenance scheduling model in order to minimize the track irregularities and mitigate the train derailment accident risk. Finally, we apply our model to decision making for yearly tamping schedule, then try to show the optimal tamping schedule obtained by the model.