A nonaqueous electrolyte secondary battery which has a positive electrode containing lithium cobalt oxide as a positive active material, a negative electrode containing a graphite material and a nonaqueous electrolyte solution containing ethylene carbonate as a solvent and which is charged with an end-of-charge voltage of at least 4.3 V. Characteristically, the battery uses, as the positive active material, lithium cobalt oxide obtained by firing a mixture of a lithium salt, tricobalt tetraoxide (Co3O4) and a zirconium compound and having particle surfaces onto which the zirconium compound adheres.