The purpose of this paper is to clarify the Japanese Imperial Naval Coalfield from aspects of laws and actual situations. In modern Japan, Nihon-Koho (the first law for the mining industries) provided that domestic mines were under the Bergregal (Kozan Ouyusei). Afterwards, the mines were gradually released to civilians, and Kogyo-Jyorei (the mining industry regulations) were enacted to promote economic activities of the liberalism in 1890. However, after the establishment of the mining industry regulations, the Imperial Naval Coalfield were treated based on the Bergregal in various situations. For example, some civilians required the government to choose them as suppliers digging the Imperial Naval Coalfield. This is because some applicants owned a coal mine near the Imperial Naval Coalfield, other applicants were the poor people around there, and others appealed to the government for the possibility of the development program. The Bergregal was seen at not only the above but also another scene. On occasion of illegal diggings of the Imperial Naval Coalfield, the Fukuoka District Court made the decision to dismiss a suit of the Department of the Imperial Navy. Therefore the Imperial Navy decided to use Choku-Rei (an Imperial Ordinance) because not affecting the limitation in the existing law including the mining industry regulations. As a result, the Imperial Navy had continued to apply the Bergregal for its coalfield.