A vehicle comprising: a control device (40, 50, 70, 80) mounted to a vehicle body; an additional device removably mountable to the vehicle body; and an existing device mounted to the vehicle body and electrically connected to the control device (40, 50, 70, 80), the existing device being different from the additional device, wherein the control device (40, 50, 70, 80) includes: an additional control section (63, 64, 65, 66) which performs a control to realize an additional function obtained by use of the additional device, when the control device (40, 50, 70, 80) determines that the additional device is connected to the control device (40, 50, 70, 80); and a change control section (62, 70, 80) which performs a control in such a manner that an existing function obtained by use of the existing device is changeable from the existing function in a state in which the additional device is not connected to the control device (40, 50, 70, 80), when the control device (40, 50, 70, 80) determines that the additional device is connected to the control device (40, 50, 70, 80), wherein the additional device required to obtain the additional function functions as a switching device for changing the existing function, characterized in that the additional device outputs a signal used in calculation or the control to realize the additional function, the signal being irrelevant to the existing function. a control device (40, 50, 70, 80) mounted to a vehicle body; an additional device removably mountable to the vehicle body; and an existing device mounted to the vehicle body and electrically connected to the control device (40, 50, 70, 80), the existing device being different from the additional device, wherein the control device (40, 50, 70, 80) includes: an additional control section (63, 64, 65, 66) which performs a control to realize an additional function obtained by use of the additional device, when the control device (40, 50, 70, 80) determines that the additional device is connected to the control device (40, 50, 70, 80); and a change control section (62, 70, 80) which performs a control in such a manner that an existing function obtained by use of the existing device is changeable from the existing function in a state in which the additional device is not connected to the control device (40, 50, 70, 80), when the control device (40, 50, 70, 80) determines that the additional device is connected to the control device (40, 50, 70, 80), an additional control section (63, 64, 65, 66) which performs a control to realize an additional function obtained by use of the additional device, when the control device (40, 50, 70, 80) determines that the additional device is connected to the control device (40, 50, 70, 80); and a change control section (62, 70, 80) which performs a control in such a manner that an existing function obtained by use of the existing device is changeable from the existing function in a state in which the additional device is not connected to the control device (40, 50, 70, 80), when the control device (40, 50, 70, 80) determines that the additional device is connected to the control device (40, 50, 70, 80), wherein the additional device required to obtain the additional function functions as a switching device for changing the existing function, characterized in that the additional device outputs a signal used in calculation or the control to realize the additional function, the signal being irrelevant to the existing function.