A torsion sensor, configured to sense torque generated or received by a joint actuator, is provided. The torsion sensor includes an inner ring, an outer ring, multiple radial bridging portions, multiple overload structures, and multiple strain sensing units. The inner ring and the outer ring are disposed on the same axis and are separated from each other. The torque enables the inner ring and the outer ring to relatively rotate with reference to the axis. The radial bridging portions are disposed at intervals and each radial bridging portion is connected between the inner ring and the outer ring along a radial direction, and each radial bridging portion has at least one depression. Each overload structure extends from the inner ring toward the outer ring along the radial direction and has at least one gap with the outer ring. The strain sensing units are respectively disposed on the radial bridging portions.