A mounting structure for a torque sensor comprising: a torque sensor comprising an annular first structure, an annular second structure having a diameter smaller than a diameter of the annular first structure and arranged concentrically with the annular first structure, a plurality of third structures connected between the annular first structure and the annular second structure and transmitting torque between the annular first structure and the annular second structure, and at least two sensor units (44, 45) provided between the annular first structure and the annular second structure; said structure being characterized by comprising: a plurality of first contact portions (61, 32c, 41d, 32d, 41e, 41f, 32e) provided on one of the annular first structure and a first attachment portion fixed to the annular first structure, wherein the first attachment portion is in a cylindrical shape, and an outer peripheral side surface of the annular first structure is in contact with an vertical inner side surface of the first attachment portion at the plurality of first contact portions (61, 32c, 41d, 32d, 41e, 41f, 32e) and except for the plurality of first contact portions (61, 32c, 41d, 32d, 41e, 41f, 32e) is not in contact with the vertical inner side surface of the first attachment portion, and a plurality of second contact portions provided on one of the annular second structure and a second attachment portion (36b-2) fixed to the annular second structure, wherein the second attachment portion (36b-2) is a shaft, and the annular second structure is in contact with an outer side surface of the second attachment portion (36b-2) at the plurality of second contact portions and except for the plurality of second contact portions is not in contact with the outer side surface of the second attachment portion (36b-2). a torque sensor comprising an annular first structure, an annular second structure having a diameter smaller than a diameter of the annular first structure and arranged concentrically with the annular first structure, a plurality of third structures connected between the annular first structure and the annular second structure and transmitting torque between the annular first structure and the annular second structure, and at least two sensor units (44, 45) provided between the annular first structure and the annular second structure; said structure being characterized by comprising: a plurality of first contact portions (61, 32c, 41d, 32d, 41e, 41f, 32e) provided on one of the annular first structure and a first attachment portion fixed to the annular first structure, wherein the first attachment portion is in a cylindrical shape, and an outer peripheral side surface of the annular first structure is in contact with an vertical inner side surface of the first attachment portion at the plurality of first contact portions (61, 32c, 41d, 32d, 41e, 41f, 32e) and except for the plurality of first contact portions (61, 32c, 41d, 32d, 41e, 41f, 32e) is not in contact with the vertical inner side surface of the first attachment portion, and a plurality of second contact portions provided on one of the annular second structure and a second attachment portion (36b-2) fixed to the annular second structure, wherein the second attachment portion (36b-2) is a shaft, and the annular second structure is in contact with an outer side surface of the second attachment portion (36b-2) at the plurality of second contact portions and except for the plurality of second contact portions is not in contact with the outer side surface of the second attachment portion (36b-2).