We developed a deterministic mathematical model to grasp transmission features of the large scale epidemic of Ebola virus disease (EVD) occurred in the West African region since March 2014. Basic reproduction number (R0) was estimated as 1.32, and the number of days between clinical onset and isolation into caretaking facilities was estimated as 5.0 days. If the days to isolation was less than 3.3 days, the epidemic was considered to be successfully controlled.