An SFA server stores a customer database. The customer database stores: a customer name and/or staff name of corresponding customer; a business transaction of the customer; detail information representing business activities for achieving the business transaction, a completion scheduled date, and an actual completion date; information for determining whether each maturity stage has been attained; a check flag representing whether a maturity item has been attained, and a strategic scenario showing some plans for the business transaction toward the customer. Each of sales-staff terminal inputs the above data, stores the input data, and displays the detail information of the business activities in chronological order of the scheduled dates in the form of a list. The displayed data can be viewed from a manager terminal as well. An SCM server estimates the demand for products, based on the check flag stored in the customer database.