Provided is an image forming system capable of updating internal data of an external device according to an instruction from a server. An app-installing unit installs an application for updating internal data of card reader in an image forming apparatus. An internal-data-updating unit causes the image forming apparatus to execute the application installed by the app-installing unit. An app-acquiring unit acquires the application from the server according to an instruction from the server. An app-executing unit executes the app acquired by the app-acquiring unit and updates the external device to the internal data. As a result, the internal data of the card reader is updated.