To provide a slim joint device capable of achieveing two degrees of freedom in one joint, and achieving complete action.

In this joint device 10, an end of an arm 1 is jointed with an end of an arm 2 so as to move to each other. Besides, a first cross gear 13, a third and a fourth gears 13, 14 are provided. The first cross gear 3 is disposed at a joint portion 1j. In the first cross gear 3, the first gear 31 and the second gear 32 share an identical center. The first and the second gears 31, 32 are spur gears. The first gear 31 and the second gear 32 cross in a cross shape. The third gear 13 which is engaged with the first gear 31 includes the arm 1. The fourth gear 14 which is engaged with the second gear 32 includes the arm 2. The arm 1 can move to the arm 2 when the third gear 13 is rotated. The arm 2 can move to the arm 1 when the fourth gear 14 is rotated.