A composite positive electrode in an all-solid-state battery is prepared by mixing LiCoO2 particles and Li2S–P2S5 solid electrolytes. Raman spectroscopy is conducted for the composite positive electrodes before and after the initial charging process. Raman spectral changes are observed, which corresponds to structural changes of LiCoO2 particles during the charge test. However, some spectra indicate that several LiCoO2 particles show no structural changes although the cell is fully charged. A local state-of-charge (SOC) distribution map of the composite electrode is obtained by Raman mapping. The mapping image after the charge test shows that distributions of reactions exist in the composite positive electrode.