A system in which a terminal device communicates with a server and processes data enables the terminal device to continue processing data even when a communication fault occurs.A data processing device has a data storage unit storing data processing device-side master data, connects through a server communication path to a server, updates the data processing device-side master data stored in the data storage unit based on server-side master data stored by the server, connects to a tablet through a process communication path, responds based on the data processing device-side master data stored by the data storage unit to a master data transmission request sent by the tablet, and receives the process information sent by the tablet.