The present invention relates to an information processing terminal that makes it possible to readily upgrade software of information processing terminals connected by a network. When a control program stored in a display apparatus 5B is upgraded by a control program stored on a memory card 10, an upgrade program for a base station 1 and the control program for display apparatus 5A and 5C read by the display apparatus 5B are transmitted to the base station 1. The base station 1 upgrades a control program stored therein by the upgrade program received by the base station 1, and also transmits the control program for the display apparatus 5A and 5C to the display apparatus 5A and 5C. The display apparatus 5A and 5C each upgrade a control program stored therein by the upgrade program received by the display apparatus 5A and 5C, respectively.