A torque detector (16) is provided with first and second units (38, 39). The first unit (38) includes a first synthetic resin (40) formed by molding a pair of magnetic flux collector rings (34A, 34B). The second unit (39) includes a second synthetic resin (41) fixed to a magnetic shield plate (37B) containing a metal; an insertion protruding part (44) arranged on the synthetic resin (41); and magnetic sensors (35A, 35B) held by the insertion protruding part (44). The first synthetic resin (40) includes a receiving plate (38a) whereupon a base (38e) for receiving the magnetic shield plate (37B) is formed. In a status where the receiving plate (38a) exists between the magnetic shield plate (37B) and an object (30) to be attached, both the magnetic shield plate (37B) and the receiving plate (38a) are fastened to the object (30) by a pair of fixing screws (32).