A torque sensor where a first rotary shaft and a second rotary shaft are disposed on a common axial line, with the first rotary shaft and the second rotary shaft being coupled together by a torsion bar, and which detects torsional torque applied between the first rotary shaft and the second rotary shaft, the torque sensor comprises: magnetic field generating means (6, 17) that generate a magnetic field in the radial direction around the common axial line and are disposed around the common axial line; magnetic field varying means that vary, in response to the relative rotation between the first rotary shaft and the second rotary shaft, the direction and magnitude of a detected magnetic flux flowing along the common axial line from the magnetic field generating means (6, 17); magnetic sensor means (15, 15a, 15b) that detects the detected magnetic flux; and an outer peripheral cylinder that rotates together with the second rotary shaft, wherein the magnetic sensor means generates an output signal whose polarity changes in response to the direction of the detected magnetic flux and whose magnitude changes in response to the magnetic flux, characterized in that the magnetic field generating means (6, 17) are disposed on the outer peripheral surface of an inner peripheral cylinder or a solid shaft between the first and second rotary shafts (1, 2), the inner peripheral cylinder and the solid shaft made from a magnetic material and coupled at one end to the first rotary shaft so as to rotate with the first rotary shaft; in that the magnetic field varying means include first, second, third and fourth magnetic field varying means (31, 32, 33, 34) disposed along and around the common axial line, wherein the first and second magnetic field varying means (31, 32) are disposed adjacent an upper end portion and a lower end portion, respectively, of the magnetic field generating means (6, 17), and the third and fourth magnetic field varying means (33, 34) are disposed on the outer sides of the first and second magnetic field varying means (31, 32) respectively; in that the outer peripheral cylinder includes first and second outer peripheral cylinders (12a, 12b) that are constructed such that the detected magnetic flux flows between them, wherein the first and third magnetic field varying means (31, 33) are disposed within an inner periphery of the first outer peripheral cylinder, and the second and fourth magnetic field varying means (32, 34) are disposed within an inner periphery of the second outer peripheral cylinder; and in that the magnetic sensor means (15, 15a, 15b) generate the output signal on the basis of the detected magnetic flux flowing through between the first and second outer peripheral cylinders (12a, 12b). magnetic field generating means (6, 17) that generate a magnetic field in the radial direction around the common axial line and are disposed around the common axial line; magnetic field varying means that vary, in response to the relative rotation between the first rotary shaft and the second rotary shaft, the direction and magnitude of a detected magnetic flux flowing along the common axial line from the magnetic field generating means (6, 17); magnetic sensor means (15, 15a, 15b) that detects the detected magnetic flux; and an outer peripheral cylinder that rotates together with the second rotary shaft, wherein the magnetic sensor means generates an output signal whose polarity changes in response to the direction of the detected magnetic flux and whose magnitude changes in response to the magnetic flux, characterized in that the magnetic field generating means (6, 17) are disposed on the outer peripheral surface of an inner peripheral cylinder or a solid shaft between the first and second rotary shafts (1, 2), the inner peripheral cylinder and the solid shaft made from a magnetic material and coupled at one end to the first rotary shaft so as to rotate with the first rotary shaft; in that the magnetic field varying means include first, second, third and fourth magnetic field varying means (31, 32, 33, 34) disposed along and around the common axial line, wherein the first and second magnetic field varying means (31, 32) are disposed adjacent an upper end portion and a lower end portion, respectively, of the magnetic field generating means (6, 17), and the third and fourth magnetic field varying means (33, 34) are disposed on the outer sides of the first and second magnetic field varying means (31, 32) respectively; in that the outer peripheral cylinder includes first and second outer peripheral cylinders (12a, 12b) that are constructed such that the detected magnetic flux flows between them, wherein the first and third magnetic field varying means (31, 33) are disposed within an inner periphery of the first outer peripheral cylinder, and the second and fourth magnetic field varying means (32, 34) are disposed within an inner periphery of the second outer peripheral cylinder; and in that the magnetic sensor means (15, 15a, 15b) generate the output signal on the basis of the detected magnetic flux flowing through between the first and second outer peripheral cylinders (12a, 12b).