To improve the satisfaction of a customer by simple operation and to easily prepare a business plan of a high added value ratio.

In order to prepare the business plan, a cash base business plan table 4 is displayed on a display device. The table 4 is provided with data on the amount of an initial balance sheet and data on a planning amount required respectively for business activity, investment activity and financial activity in order respectively as a data input section by each of a plurality of account headings required in the balance sheet and an income statement. Data on an amount is inputted to a corresponding data input section in the table 4 displayed by the display device by an input device. Thus, data is calculated and displayed by each corresponding account heading in a predictive income statement and a predictive balance sheet.