A rotation drive device includes a crankshaft which has two ends dynamically connected to a drive source and a driven device, respectively. The drive source drives the crankshaft to rotate the driven device. The crankshaft structurally changes to make the two ends of the shaft portion connected to the rotation drive portion and the driven portion, respectively, at different central angles, which divides the space into two subspaces which are located two sides of the shaft portion, so that the wire can be arranged in the subspaces at both sides of the shaft portion, thus enhancing the flexibility of wire distribution while improving rotation range of motion.