PURPOSE: To prevent destruction of a network due to a mobile station and to attain early discovery of a fault of a mobile station especially in the mobile radio communication system.

CONSTITUTION: A base station 1 making line changeover, frequency measurement and command of function check makes a function check command to a mobile station 8. The mobile station 8 executes a function check and sends the result to the base station 1. Upon the receipt of the result, the transmission frequency of the mobile station 8 is measured. The base station 1 analyzes the check result and the result of frequency measurement and commands the transmission stop and inhibit to the mobile station 8 when the result is defective. The similar operation is available even when a transmission function has a fault.