When a layered rock-salt type cathode active material and a sulfide solid electrolyte are mixed to be a cathode mixture, and an all solid-state battery is obtained using this cathode mixture, oxygen is released from the cathode active material when the all solid-state battery is charged, and the sulfide solid electrolyte is oxidized, which results in increase of the internal resistance of the all solid-state battery. To increase the concentration of cobalt inside the layered rock-salt type cathode active material to secure a high capacity, and at the same time to lower the concentration of cobalt of the surface of the cathode active material, to suppress release of oxygen in charging, specifically, a cathode mixture for an all-solid-state battery includes: a cathode active material; and a sulfide solid electrolyte, wherein the cathode active material has a layered rock-salt crystal phase, and consists of a composite oxide containing Li, Ni, Co, and Mn, and the concentration of cobalt inside the cathode active material is higher than that of a surface of the cathode active material.
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