A torsion sensor, including a casing assembly, a sleeve set, a driven slider, a driving slider, an elastic member, a magnetic sensor, and a magnetic member is provided. The sleeve set includes a first sleeve, a second sleeve, and a third sleeve. The first sleeve is disposed in the casing assembly. The second sleeve has a neck portion sleeved on the second side of the first sleeve. The third sleeve is disposed between the first and the second sleeves. The driven slider is connected to a head portion of the second sleeve. The driving slider surrounds an outer side of the driven slider. The elastic member surrounds an outer side of the second sleeve. One of the magnetic sensor and the magnetic member is disposed in the casing assembly, and the other one is disposed in the sleeve set. The magnetic sensor and the magnetic member are disposed opposite to each other.