Owing to the detailed geological, petrological, and geochronological studies of the Ayukawa-Sanbagawa area (the type locality of the Sanbagawa metamorphic belt), Kanto Mountains, it is clarified that the Sanbagawa metamorphic belt consists of several geological units. The gap of the detrital zircon U-Pb ages and the phengite K-Ar ages of each unit of the metamorphic rocks indicate that these units have individually different sedimentation age and timing of exhumation. The Sanbagawa metamorphic belt has not coherent structure, and has a character of "diachronous-progressive metamorphism". It is presumed that the formation mechanism of metamorphic mineral zoning of the Sanbagawa belt is formed by the "Two way street model" tectonics.