AbstractWe have observed and recorded the neutral current of a 500‐kV transformer at a substation in the Chubu region since 2008 in order to detect electromagnetic anomalies associated with earthquakes. In this study, we could not find any particular anomalous change of the neutral current before and after earthquakes (e.g., for the Suruga Bay Earthquake of August 11, 2009). However, from the results of a quantitative analysis between geomagnetic field data and neutral current data, we would be able to investigate the underground electric conductivities near the substations. It would be possible to monitor changes of subsurface electromagnetic structure before and after earthquakes. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 183(1): 32–38, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22297