A sensor device comprising: a permanent magnet attached to a first shaft and magnetized in a circumferential direction; a magnetic yoke that is fixed to a second shaft coupled to the first shaft via a coupling shaft and is disposed in a magnetic field formed by the permanent magnet ; a first magnetism collection ring disposed so as to surround the magnetic yoke and configured to collect magnetic flux of the magnetic yoke ; a first holder that holds the first magnetism collection ring ; a second magnetism collection ring disposed side by side with the first magnetism collection ring in an axial direction of the second shaft , disposed so as to surround the magnetic yoke , and configured to collect the magnetic flux of the magnetic yoke ; a second holder disposed side by side with the first holder in the axial direction and configured to hold the second magnetism collection ring ; and a magnetic sensor that detects magnetic flux of a magnetic circuit formed by the permanent magnet , the magnetic yoke , the first magnetism collection ring , and the second magnetism collection ring , wherein the magnetic sensor is disposed between the first magnetism collection ring and the second magnetism collection ring with the magnetic sensor integrally assembled to the second holder , characterized in that the magnetic sensor is mounted on a circuit portion ; the circuit portion is provided with a through hole that penetrates the circuit portion in a plate thickness direction; the second holder is provided with a positioning protrusion that extends toward the first holder ; and the positioning protrusion provided on the second holder is inserted through the through hole of the circuit portion . a permanent magnet attached to a first shaft and magnetized in a circumferential direction; a magnetic yoke that is fixed to a second shaft coupled to the first shaft via a coupling shaft and is disposed in a magnetic field formed by the permanent magnet ; a first magnetism collection ring disposed so as to surround the magnetic yoke and configured to collect magnetic flux of the magnetic yoke ; a first holder that holds the first magnetism collection ring ; a second magnetism collection ring disposed side by side with the first magnetism collection ring in an axial direction of the second shaft , disposed so as to surround the magnetic yoke , and configured to collect the magnetic flux of the magnetic yoke ; a second holder disposed side by side with the first holder in the axial direction and configured to hold the second magnetism collection ring ; and a magnetic sensor that detects magnetic flux of a magnetic circuit formed by the permanent magnet , the magnetic yoke , the first magnetism collection ring , and the second magnetism collection ring , wherein the magnetic sensor is disposed between the first magnetism collection ring and the second magnetism collection ring with the magnetic sensor integrally assembled to the second holder , characterized in that the magnetic sensor is mounted on a circuit portion ; the circuit portion is provided with a through hole that penetrates the circuit portion in a plate thickness direction; the second holder is provided with a positioning protrusion that extends toward the first holder ; and the positioning protrusion provided on the second holder is inserted through the through hole of the circuit portion . <EOS>