Magnetic matter such as transition metals or metal oxides are able to exhibit ferromagnetism by the clustering in magnetic semiconductors. We fabricated Co-doped ZnO samples using the sol-gel method, and studied the magnetic precipitates in the samples by using both neutron diffraction and X-ray absorption fine-structure measurements. The structural details were characterized by X-ray and neutron diffraction, and the data were interpreted using Rietveld refinement. The doped Co ion was fully substituted into a ZnO lattice at 5 mol%, but the secondary phase of the Co3O4 was formed above 5 mol% of Co doping and its neutron diffraction signal increased up to 20 mol%. The quantitative amounts of each phase were calculated to be 55.43 wt.% of Co3O4 and 44.57 wt.% of fully cobalt-substituted ZnO. In the 30 mol% Co-doped sample, Co metal, as well as oxidized Co, were identified in this study. Those signals, however, were not observed by X-ray diffraction. To verify the local chemical bonding state, we used extended X-ray absorption fine-structure measurement and investigated the formation of precipitates by calculating the inter-atomic distance using Fourier analysis.