A multi-joint synchronous rotary axle structure includes a middle shaft and two parallel side shafts at two sides of the middle shaft. A first synchronous actuating assembly and a second synchronous actuating assembly are provided at two opposite positions of the middle shaft and the side shafts, which are connected in a reverse link relationship. The two side shafts can be rotated about the middle shaft to generate a synchronous reverse turning. A two-way shaft plate is provided between the middle shaft and each of the side shafts to provide the torsion of tuning so as to form a compact multi-joint synchronous rotary axle structure.