The present invention relates to a dispersant for a positive electrode of a power storage device. The dispersant is a copolymer that contains a constitutional unit A represented by the following general formula (1) and at least one constitutional unit B selected from the group consisting of a constitutional unit B1 represented by the following general formula (2) and a constitutional unit B2 represented by the following general formula (3). The total content of the constitutional unit A and the constitutional unit B in the copolymer is 80% by mass or more. The content of the constitutional unit A in all constitutional units of the copolymer is 35% by mass or more.