An information processing apparatus is included that is installed to an operator connected to a portable terminal apparatus by a communication line and is connected by a network to a plurality of operators selectable as a roaming destination of the portable terminal apparatus. The information processing apparatus includes a database that stores operator information, and an information distributing unit that, in response to receiving specification of an area of the roaming destination from the portable terminal apparatus, reads from the database operator information on an operator having a service area thereof in the specified area and distributes the read information to the portable terminal apparatus. The portable terminal apparatus includes a storing unit that stores the operator information and an information processing unit that receives the distribution of operator information on the operators having service areas thereof in a specified area by specifying the area of the roaming destination and registers the operator information in the storing unit.