The copper deposits of Ashio Mine occur both in rhyolite and in Paleozoic chert beds, the latter having received folding and faulting. In this essay, the writer demonstrated the intimate relation between geological structure and mineralization, in the Arikoshi syncline. Bonanzas or shoots in chert are concluded to have been formed mainly either by the metallization along the intersection lines of shear veins or along the folding axes, mainly synclinal axes, which plunge into the sufficient source of mineralizing solution.