To provide an external fixation device without the need of time and labor for an operation, for which the mental care of a patient is taken into consideration, and a piercing pin attaching / detaching joint.

For the external fixation device 1, a plurality of supporting bodies 2 and 3 for freely attachably and detachably holding piercing pins P1 and P2 are connected through a length-adjustable connection shaft 4. The connection shaft 4 is provided with a bag-like nut 6 for which one spherical body S1 is connected through a narrow neck part N to one end and a screw hole 5 is opened at the other end, a screw shaft 7 whose one end is screwed to the screw hole 5 of the bag-like nut 6 and whose other end is connected to the other spherical body S2 through the narrow neck part N, and a lock nut 8 for tightening the screw shaft 7 to the bag-like nut 6. The supporting bodies 2 and 3 are provided with spherical recessed parts 9 and 10 where the spherical bodies S1 and S2 are sunk in and fixing means 11 and 12 for fixing the spherical bodies S1 and S2 on the inner side of the spherical recessed parts 9 and 10.