To display the operating states of a connecting device provided between the right and left wheels of a car, and fitted with an electric motor and a switching mechanism for arbitrarily switching a state of assisting the states of a car by transmitting torque to the right and left wheels from the electric motor, and a state of assisting the slewing of the car, and to enhance the characteristics of commodity.

When a switching mechanism is in a switched state of transmitting torque in the same direction of rotation to the right and left wheels from an electric motor, i.e., at a state assisting time, only lamps I of the central indicator 25M of a display means 24 corresponding in number to the current value of the electric motor, are turned on. Then, when it is in a switched state of transmitting torque to one of the right and left wheels for increasing its speed with respect to the other rear wheel from the electric motor, i.e., at a slew assisting time, only lamps I of an indicator to be an external wheel side out of the right and left indicators 25L, 25R corresponding in number to the current value turned on, and operating states of a connecting device is displayed.