PURPOSE: To prevent deterioration of an S/N ratio of an entire system by forming a thin-film wiring which is lead from two electrode parts of a SQUID ring in a twist-pair structure by multilayering on a substrate.

CONSTITUTION: When wirings 11b and 12b from a lower electrode 11 and an upper electrode 12 are formed in a twist-pair structure, a current is induced at the wirings 11b and 12b in a direction of an arrow 31 when a magnetic flux intrudes this twist pair from an outside due to a magnetic field, etc., which is generated by a feedback current flowing at a wiring of a modulation coil 3. However, this induced current flows in opposite directions alternately in the wirings 11b and 12b so that it is canceled out within the wirings 11b and 12b, thus enabling influence of the magnetic flux to be extremely small. Therefore, deterioration of the S/N ratio as an entire system can be prevented.