To provide a differential gear having a simple structure and no fear of the action of a centrifugal force on a counter rotating member.

A differential gear comprises an input rotary shaft equipped with a main rotating member, a counter rotating member for transmitting rotary power of the main rotating member in a state of revolution around the axial line of the input rotary shaft or a static state, a rotary shaft for supporting a counter member and an output rotary shaft including a driven rotary member to which a final rotary power of the counter rotary member is transmitted. While a revolution speed of the counter rotating member increases as decreasing the rotation speed of the output rotary shaft in comparison with the rotation speed of the input rotary shaft, an inertia force produced by rotation is given to a part or all of these counter rotating members or a rotary, or non-rotary inertia body such as a flywheel or weight which revolves and/or rotates together with the counter rotating members is also included.

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