A secondary cell is provided that enables cost reduction and stable operation with a simple configuration and greatly exceeds the capacity of a lithium-ion cell. In a secondary cell, a conductive first electrode is formed on a substrate. An n-type metal oxide semiconductor layer, a charging layer for charging energy, a p-type metal oxide semiconductor layer, and a second electrode are laminated. The charging layer is filled with an n-type metal oxide semiconductor of fine particles. By a photoexcited structural change phenomenon caused by ultraviolet irradiation, a new energy level is formed in a band gap of the n-type metal oxide semiconductor. An electron is captured at the newly formed energy level, thereby charging energy. The charging layer is charged by connecting a power source between the first electrode and the second electrode. It is also possible to charge energy by light, using a transparent electrode.