PURPOSE: To release a driver from troubles to operate each operating switch for various operating devices and allow a safety driving of a vehicle by a method wherein a multitude of various operating devices mounted on the vehicle are controlled by a sound of commanding voice from the driver.

CONSTITUTION: When an operating switch 3 is closed and a driver voices a predetermined voice coincided with a voice pattern memorized in a memory 2a of a decision circuit 2, a regulating portion 2c of the decision circuit 2 regulates an electric signal from a microphone 1 into a signal for comparison in a comparing portion 2b, and when the memory 2a and the regulating portion 2c are coincided, the decision circuit 2 derives a control signal and operates an operating device 5 through a relay 4. If the driver voices a voice except the predetermined voice, the decision circuit 2 will never derive the control signal and the operating device 5 will never be operated.