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.