Thinking of Inventory Control Method from the standpoint of order, it can ve divided into Fixed Size Ordering System and Fixed Period Ordering System. Both are the same in that Safety Stock is always prepared. Focusing on the order quantity and time, however, in Fixed Size Ordering System a certain quantity of orders are issued but the time and period for order are unstable, and it is also called Order Point Method because it is based on the order point. On the other hand, in Fixed Period Ordering System, orders are issued according to pre-set time and period, but the quantity of orders is unstable. These methods are also called Statistical Inventory Control Method where the quantity and period are operated and controlled as standards of order by setting them based on the past usage. This method features dependently and individually controlling target items.