A reel device of diversion joint comprises: a casing, a wire holder, a telegraph line, a position plate and two L-shape anchors. The casing has a shaft and a restraint cavity. The wire holder is located on the shaft. The telegraph line is winded inside the wire holder. The position plate located on the wire holder has a guiding groove and at least one anchor recess. Two L-shape anchors located on the guiding groove are separated to two sides of the shaft, and each of the L-shape anchors has a slider protrusion to slide along the guiding groove. When the joint performs a linear motion, the wire holder drives the shaft to rotate and the slider protrusion slides along the guiding groove. When the linear motion stops, the joint is fixed on a position where the slider protrusion is anchored in the anchor recess.