The present invention relates to a power storage device including: a positive electrode having a positive-electrode current collector, a positive-electrode active material with a plurality of first projections on the positive-electrode current collector, and a first insulator on an end of each of the plurality of first projections; a negative electrode having a negative-electrode current collector, a negative-electrode active material with a plurality of second projections on a surface of the negative-electrode current collector, and a second insulator on an end of each of the plurality of second projections; a separator between the positive electrode and the negative electrode; and an electrolyte provided in a space between the positive electrode and the negative electrode and containing carrier ions. In each of the first projections and the second projections, a ratio of the height to the width is 3 or more and 1000 or less to 1, i.e. (3 to 1000):1.