A navigation server and the like capable of improving determination accuracy of advertisement effectiveness is provided. According to a navigation system of the present invention, it is determined whether or not one or a plurality of time in which a position of a navigation device 200 (an user or a vehicle 2) at each time satisfies “a first condition” in relationship with a position of a business operator satisfies “a second condition” in relationship with a temporal factor with respect to business transaction of the business operator. Thereafter, according to the determination result, an interest level of the user with respect to the business operator and the like is evaluated as “a third index value”.