To provide a radio communication system capable of further improving security of communication contents by devising a method of modifying an encryption key.

When an application 4c of STA4-1 is activated, a printer driver 4b starts and print data are transmitted from an STA radio communication unit 4a to an AP radio communication unit 1a-1 of an AP 1-1. The print data are transmitted to a printer 2 via a radio LAN 3, and the printer 2 starts desired printing. Then, for example, upon completion of printing of one page, a request of exchanging the encryption key is transmitted from the STA4-1 to AP1-1. In this way, the AP1-1 executes exchange of the encryption key for the STA4-1. Further, upon completion of printing of subsequent one page, the STA4-1 re-transmits a request of exchanging the encryption key to the AP1-1, the AP1-1 re-executes the exchange of the encryption key to the STA4-1, and the encryption key is exchanged per printing page until printing is completed.