A torque sensor to detect torque transmitted by a shaft having magnetostrictive properties is provided with a pair of cylindrical detection units arranged around the shaft and aligned side-by-side in an axial direction of the shaft, and first and second connection lines connecting the pair of detection units. Each detection unit includes first to fourth detection coils stacked in a radial direction. A series circuit formed by series connecting the first and fourth detection coils is parallel connected to a series circuit formed by series connecting the second and third detection coils. The first and second connection lines are configured to connect between corresponding connecting portions of the first and fourth detection coils and between corresponding connecting portions of the second and third detections coils, respectively. The torque transmitted by the shaft is detected based on a potential difference between the first connection line and the second connection line.