Since the word of Jingikan appears in historical documents before the Taiho ritsuryo (Taho Code) was established, it is considered that it had been established in the Asukakiyomihara-ryo, etc., but details of the government systems before the Taiho ritsuryo are not known because no original documents from those eras remain.
大宝律令制定以前の史書にもその存在が現れるため、飛鳥浄御原令等によって既に設置されていたと考えられているが、原文が残っていないため、大宝律令以前の制度については詳細は定かではない。