An anode active material–semiconductor hybrid electrode was prepared by combining electroplated Co and a GaP single crystal. This hybrid electrode acts not only as an active material for a cobalt–air cell but also as a photo-electrode for storing light energy. We studied the photo-electrochemical properties of the hybrid electrode, and confirmed that the electrode’s oxidized Co layer was reduced by the electrons generated when the GaP side was illuminated. We assembled a GaP–Co|KOH|O2 cell with only two electrodes: the above hybrid electrode and an air electrode (oxygen catalyst). The photo-electrochemical characteristics of the Co–GaP hybrid electrode and cobalt–air cell showed that this cell can be charged by illuminating it and discharged by using the oxygen in the air.