To enhance cycle characteristics and capacity of an electrode active material including sulfur.

A power storage device includes carbon and sulfur as principal components, the content of sulfur is more than 38 wt.% to 70 wt.% or below, and a polycyclic aromatic compound with a thiophene structure in a skeleton is used for the electrode active material. It is preferable that the polycyclic aromatic compound has a polythienoacene structure including sulfur, and it is preferable that an element ratio S/C of sulfur to carbon is 0.40 to 0.70. The electrode active material can be manufactured in a production process of producing the polycyclic aromatic compound with the thiophene structure in the skeleton by performing treatment of: mixing at least one of an aliphatic polymer compound having a straight chain and a polymer compound having a thiophene structure and sulfur; heating them at an inert atmosphere; and removing excessive sulfur.

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