During the 2020–2021 winter season, we detected 6 gamma‐ray glows at Kanazawa University, Japan. Negative surface electric fields (E‐fields; in the sign convention of atmospheric electricity) were observed by a field mill during all the glow cases. In five of the six cases, the peak E‐field reached around −12 kV m−1, and the E‐field during the glow detection was the strongest in the interval including 3 hr before and after the detection time. Therefore, negative charges should have been dominant in the thunderclouds that produced the gamma‐ray glows, and electrons were probably accelerated and multiplied by the E‐fields between a predominantly negative charge layer and a localized positive charge layer below. In addition, we extracted 8 non‐detection cases in the 2020–2021 winter season, in which surface E‐fields were stronger than −12 kV m−1. In 5 of the 8 cases, radar echoes were inadequately developed, suggesting insufficient charge accumulation. On the other hand, the remaining 3 cases had well‐developed radar echoes, and there was no significant difference from the detection cases. Plain Language Summary Gamma‐ray glow is a minute‐lasting burst of high‐energy photons associated with thunderclouds. High‐energy photons are considered to originate from high‐energy electrons accelerated and multiplied in strong electric fields inside thunderclouds. When a gamma‐ray glow is detected on the ground, electrons are considered to be accelerated downward by upward electric fields. In the 2020–2021 winter season, we detected a total of 6 gamma‐ray glows during winter thunderstorms at Kanazawa University, Japan. An electric‐field monitor recorded negative electric fields at the surface during all the glow detections, indicating negative charges overhead. It suggests that the thunderclouds that produced the gamma‐ray glows were strongly charged negatively, and a localized positive charge layer existed in the lower part to produce an upward electric field for downward electron acceleration. Key Points In the 2020–2021 winter season, 6 gamma‐ray glows were detected at Kanazawa University, Japan, with electric‐field measurement Surface electric fields were negative during the detection of all the gamma‐ray glows High‐energy electrons seemed to be produced between a well‐developed negative charge region and a localized positive charge region below