PURPOSE: To provide a TV game radio transmission device for enabling cordless operation by means of radio transmission of an output signal from game machine main body to a TV set, a radio transmission adapter, and a game cassette equipped with a radio transmission antenna.

CONSTITUTION: The adapter RF input terminal 3 and adapter power output terminal 5 of a radio transmission adapter 1 are connected to the RF output terminal 51 and DC power input terminal 53 of a game machine main body 10, respectively, and thereby an RF signal input from the game machine main body 10 can be subjected to high-frequency amplification and be transmitted by radio using a transmitting antenna 9 to a feeder or an indoor antenna connected to a TV set. Thus, the radio transmission adapter 1 can be attached to even an existing game machine main body 10 which is connected by line and thereby cordless operation is made possible without providing any special receiving portion to the TV set.