A mobile terminal device has an information processing unit that processes electronic money information and a storage unit that stores the electronic money information. A receiving unit receives from an electronic money server an electronic money identification (ID), a mobile terminal identification (ID) identifying the mobile terminal device, and a money information processing program for enabling the information processing unit to execute processing of the money information stored in the storage unit. An installation unit installs into the storage unit the money information processing program and the IDs received by the receiving unit. A sending unit sends to the electronic money server information necessary for enabling the electronic money server to provide electronic money service, the necessary information being sent to the electronic server before the receiving unit receives the money information processing and the IDs.