A voice control system is directed to a car navigation device that includes: a display unit; a microphone; a speech recognition unit for recognizing, as a command, a speech uttered by a user; and a navigation ECU to which the voice recognition unit outputs the command. When the user inputs the speech, auxiliary switches are shown on the display unit. When the user selects one of the auxiliary switches, respective functions that correspond to the auxiliary switches are executed. The functions include displaying a voice command list or guidance for voice input on the displaying unit or outputting, to the navigation ECU, a result of determination whether a certain function, such as setting of a destination, should be allowed to be executed, the user first being required to affirm or negate the recognized destination setting by voice or auxiliary switch.