To provide a composite card type radio apparatus capable of minimizing the influence of noise generated from an information processor and highly holding the quality of communication as a radio MODEM.

The card type radio apparatus 1 is inserted into a slot 21 of a personal computer(PC) 20. An insertion judging part 16 detects the insertion and an antenna 11 is switched to a mono-pole antenna 12 for radio communication. Information 21 wirelessly transmitted from the external is received by a radio part 14 through the antenna 12. The electric field strength of an antenna receiving radio wave is detected at specified frequency to detect a synchronizing signal. When the field strength is a prescribed value or more and the synchronizing signal is detected, the radio wave is regarded as a receivable radio wave and the PC 20 is notified of the state. Thereby the PC 20 executes radio communication by using the frequency. When the field strength and the synchronizing signal are insufficient, reception based on another different frequency is started. Since communication is executed at optimum receiving frequency, the quality of communication can be improved.