A SQUID is a highly sensitive magnetic sensor. However, a defect of SQUID is high susceptibility to magnetic noise. The high robustness of SQUID with respect to magnetic noise enables to widen the range of applications. We have striven to clarify the mechanism of weakness in magnetic noise by means of numerical electromagnetic field simulation to support a SQUID development. However, a Josephson junction was modeled as a constant resistance and a SQUID behaviour was not correctly simulated in the previous paper. Therefore, the non-linear current-voltage characteristic of the Josephson junction is newly taken into account the simulation to represent the SQUID behaviour. As the results, the phenomena of the step-increasing magnetic flux and the spike voltage that could not be reproduced in the previous paper is simulated. It is successful to qualitatively evaluate the SQUID behaviour, i.e. it becomes possible to represent superconducting-to-voltage and voltage-to-superconducting state transitions.
