An electrode active material for a power storage device of the invention includes an organic compound having, in the molecule, a plurality of electrode reaction sites and a linker site. The electrode reaction sites are residues of a 9,10-phenanthrenequinone compound that contributes to an electrochemical redox reaction. The linker site is disposed between the plurality of electrode reaction sites, does not contain any ketone group, and does not contribute to the electrochemical redox reaction. The electrode active material for a power storage device of the present invention is inhibited from being dissolved in an electrolyte and has a high energy density. By using the electrode active material, it is possible to obtain a power storage device having a high energy density and excellent charge/discharge cycle characteristics.