The sedimentary complex of the Northern Subbelt of the Chichibu Belt in the Kanto Mountains is structurally divided into three geologic units, namely the Nishimikabo, Kashiwagi, Mamba-Kamiyoshida Units in ascending order. Radiolarians from the Mamba-Kamiyoshida Unit indicate the Middle Jurassic age. The Nishimikabo Unit is in fault contact with the Kashiwagi Unit. The Kashiwagi Unit is also in fault contact with the Mamba-Kamiyoshida Unit. These moderate to low angle faults strike WNW-ESE and dip southward. There is a possibility that the Mamba-Kamiyoshida Unit is thrust over the Kashiwagi Unit. The Nishimikabo Unit is composed mainly of mudstone with turbidite origin sandstone blocks, and these sediments are regarded as submarine slide deposits. The Kashiwagi Unit is composed of acidic tuff, chert and mudstone, and these sediments are regarded as pelagic and hemipelagic sediments. The Mamba-Kamiyoshida Unit is lithologically divided into the Mamba and the Kamiyoshida Subunits in ascending order. The Mamba Subunit is conformably overlain by the Kamiyoshida Subunit. The Mamba Subunit is composed mainly of basic tuff with limestone blocks and the Kamiyoshida Subunit is composed mainly of mudstone with chert and limestone blocks. These sediments could be submarine slide deposits with allochthonous blocks. It is interpreted that each geologic unit was deposited in a distinct sedimentary environment in the Northern Subbelt of the ChichibuBelt along the Kanna River. In reference to past problems in this area, the Sakahara Formation is correlated with the Kashiwagi Unit, The sedimentary complex of Northern Subbelt of Chichibu Belt is folded by WNW-ESE trending folds in general and the Chichibu Belt is in fault contact with the Sambasfawa Belt.