Abstract: The object of the present invention is to provide technology that enable the securities firm to appropriately execute trading orders of the odd lot without making the price fluctuation risk and etc. come to the surface. First, odd lot buying orders or odd lot selling orders for a particular stock company is received (step S5). Next, it is judged whether or not the number of total buying order stocks of the odd lot or the number of total selling order stocks of the odd lot exceeds a predetermined threshold that is determined according to a predetermined rule (step S9). If it is judged that the number of total buying order stocks of the odd lot or the number of total selling order stocks of the odd lot exceeds a predetermined threshold that is determined according to a predetermined rule, a buying order of the round lot stock number defined for the particular stock company for the odd lot buying orders, a selling order of the round lot stock number for the odd lot selling orders is executed (step S11).