International guidelines that aim to protect people from adverse health effects of exposure to magnetic fields (MF) have been established by international organizations such as the International Commission on Non-Ionizing Radiation Protection (ICNIRP) or the Institute of Electrical and Electronic Engineers (IEEE). In these guidelines, one of the target effects below 100 kHz is nerve stimulation based on a few perceptual studies. Because of a few studies, the value of basic restriction of the guidelines adopt extrapolation widely such as 45 Hz to 400 Hz and 7 kHz to 100 kHz. Therefore, determination of threshold value among extrapolated frequencies is important for verification and improving of the current basic restriction. Here, we report progress of our study to determine threshold value of nerve stimulation by magnetic or electric field in in vitro.