A positive electrode for a secondary battery and a secondary battery. A mixture of at least a lithium metal oxide with a hexagonal crystal structure (belonging to the R3m space group) containing nickel (Ni) and a lithium manganese oxide with a rhombic crystal structure (belonging to the Pmmn space group) is used for the positive electrode active material. Furthermore, it is preferable for the lithium metal oxide described above to include manganese (Mn) and more preferable for cobalt (Co) to be included to improve the stability of the crystal structure. In addition, it is preferable for the proportion of the lithium manganese oxide in the mixture described above to be from 20% by weight to 80% by weight.