To provide a radio communication adapter which shares data of the radio communication adapter with a game machine without spending communication cost at a high speed, and to provide a data compression device.

This radio communication adapter 100 performs radio communication with a game machine 200 which performs a game process by a game program, and a cellular phone 300. The radio communication adapter 100 is equipped with a communication means which performs the transmission/receipt of data being processed by the game program with the game machine 200, and the cellular phone 300. The radio communication adapter 100 performs the relaying of the data between the game program which is operated on the game machine 200 and a game program which is operated on the cellular phone 300. By this constitution, the game machine 200 can share the data with the cellular phone 300.