In a magnetometer comprising a plurality of superconducting loops, each having a magnetic flux detecting coil, and a SQUID connected to the superconducting loop via magnetic flux,
- variable negative inductance generating means having two terminals for generating a negative inductance between said terminals being provide din the respective superconducting loops, said negative inductance generating means comprising at least one of a Josephson device and a direct current source for applying a direct current bias magnetic flux to the Josephson device and said negative inductance being defined by that the value of the derivative of generalized magnetic flux between said two terminals with current flowing between the terminals, that is, (d.phi./dI0 is negative, whereby the sensitivities of detection coils are equalized and intensified by adjusting the negative inductances.