A mobile terminal is notified of information indicating that an operator pack or the like is downloadable, without need for a user of the mobile terminal to perform any active operation and without need for the mobile terminal to be preliminarily equipped with an extra function for automatic installation. An installation notification system 10 of the present invention includes a mobile terminal 50 and an installation notification server 60 and is provided with an operator pack presence determining unit 15 configured to determine whether an operator pack is present in the mobile terminal 50, based on originating data sent from the mobile terminal 50, and an installation notifying unit 18 configured to notify the mobile terminal 50 of installable information indicating that the operator pack is installable, when the operator pack presence determining unit 15 determines that the operator pack is absent.