To avoid to wait for information with a frequency that the other terminals use when a terminal rises in a radio exchange system having one main device executing exchange and one or plural terminals and using a frequency hopping system.

Functions for transmitting/receiving control information are provided for the main device 1 and the respective terminals 3, 4 and 5. Functions for executing the carrier-sensing of respective radio channels for prescribed when the terminals rise are provided for the terminals. A frequency which is not carrier-detected is selected as the frequency for waiting for control information transmitted from the main device 1 by hopping in the beginning. Then, the frequency for waiting for control information is decided among several frequency bands which are not carrier-sensed in the beginning based on ID given to the respective terminals 3, 4 and 5.