A torque sensor comprising: a housing having an inner peripheral surface; a torsion bar inserted into the housing, the torsion bar having a rotation axis; a magnetic force generating part configured to rotate together with an end of the torsion bar and generate a magnetic flux in a direction of the rotation axis; a rotating magnetic circuit configured to rotate together with another end of the torsion bar; an annular groove (31, 32) formed on the inner peripheral surface of the housing to surround the rotating magnetic circuit; a magnetic collecting ring (91, 92) fitted into the annular groove (31, 32), the rotating magnetic circuit being configured to transmit the magnetic flux generated by the magnetic force generating part to the magnetic collecting ring (91, 92) in accordance with relative rotation positions of the magnetic force generating part and the rotating magnetic circuit; the magnetic collecting ring (91, 92) comprises a C-shaped ring that has a slit (91 a, 92a), the C-shaped ring having a greater diameter than the annular groove (31, 32) and being configured to decrease the diameter when fitted into the annular groove (31, 32); a staking part (33, 34) formed on the inner peripheral surface of the housing in the vicinity of the annular groove (31, 32) so as to fix the magnetic collecting ring (91, 92) into the annular groove (31, 32); and a magnetic sensor configured to detect a magnetic flux density in the magnetic collecting ring (91, 92), characterized in that the inner peripheral surface of the housing being configured to deform towards the interior of the annular groove (31, 32) and engage with the C-shaped ring on both sides of the slit (91 a, 92a). a housing having an inner peripheral surface; a torsion bar inserted into the housing, the torsion bar having a rotation axis; a magnetic force generating part configured to rotate together with an end of the torsion bar and generate a magnetic flux in a direction of the rotation axis; a rotating magnetic circuit configured to rotate together with another end of the torsion bar; an annular groove (31, 32) formed on the inner peripheral surface of the housing to surround the rotating magnetic circuit; a magnetic collecting ring (91, 92) fitted into the annular groove (31, 32), the rotating magnetic circuit being configured to transmit the magnetic flux generated by the magnetic force generating part to the magnetic collecting ring (91, 92) in accordance with relative rotation positions of the magnetic force generating part and the rotating magnetic circuit; the magnetic collecting ring (91, 92) comprises a C-shaped ring that has a slit (91 a, 92a), the C-shaped ring having a greater diameter than the annular groove (31, 32) and being configured to decrease the diameter when fitted into the annular groove (31, 32); a staking part (33, 34) formed on the inner peripheral surface of the housing in the vicinity of the annular groove (31, 32) so as to fix the magnetic collecting ring (91, 92) into the annular groove (31, 32); and a magnetic sensor configured to detect a magnetic flux density in the magnetic collecting ring (91, 92), characterized in that the inner peripheral surface of the housing being configured to deform towards the interior of the annular groove (31, 32) and engage with the C-shaped ring on both sides of the slit (91 a, 92a).