An object is to provide a service providing method capable of curbing rise of cost. A service providing method according to the present invention is one for providing services A and B, which authenticates a user of an authentication requesting terminal in order to make service A available to the user and which determines whether service B is available to the user, in a state in which the user is authenticated about service A. When service B is determined to be available, a permission message is stored and a permission response based on the permission message for utilization of service B is transmitted to the authentication requesting terminal. Then the permission message on which a utilization request message from a service utilizing terminal is based, is verified, and, if it is in an available status, the service utilizing terminal is permitted to utilize service B. The use of the authentication result on service A obviates a need for provision of new authentication means for service B, so as to lead to reduction of cost.