A positive electrode for an energy storage device according to an aspect of the present invention includes a positive active material layer, the positive active material layer contains positive active material particles and a binder, the positive active material particles contain a nickel-containing lithium transition metal composite oxide that has an α-NaFeO2-type crystal structure, the positive active material particles are at least one of: primary particles that are not substantially aggregated; and secondary particles that have primary particles aggregated, with the ratio of the median size to the average primary particle size being 5 or less, the product of the median size and BET specific surface area of the positive active material particles is 1.3 [μm m2/g] or more and 4.0 [μm m2/g] or less, and the binder has a weight average molecular weight of 500,000 or more.