Use of a nonionic dispersant for dispersing a dispersoid in water, the nonionic dispersant comprising: a polyalkylene oxide having a structural unit of the following chemical formula: where in the chemical formula, L 1 is a straight-chain alkylene group in which at least one hydrogen atom is substituted with Z-Ar, and L 1 may or may not have a substituent other than Z-Ar, L 2 is a straight-chain alkylene group in which at least one hydrogen atom may or may not be substituted with a substituent, there may be one or more Z-Ar's, and when there are a plurality of Z-Ar's, they may be the same or different from each other, Z is a linking group that links L 1 and Ar, and the linking group may or may not contain each of an alkylene chain, an ether bond, an ester bond, and an imide bond, Ar is represented by the following chemical formula,, or; there may be one or more Ar's for one Z; when there are a plurality of Ar's, they may be the same or different from each other; and a naphthyl group in the following chemical formula may be either a 1-naphthyl group or a 2-naphthyl group, R 1, R 2, and R 3 are each a substituent; there may be one or more of each of R 1, R 2, and R 3, or R 1, R 2, and R 3 each may not be present; and when there are a plurality of R 1 s, R 2 s, and R 3 s, R 1 s, R 2 s, and R 3 s may be the same or different from each other, respectively, n and m are each an integer of 1 or more, a sequence of L 1 and L 2 may be any of alternating, random, or block sequences, and there may be one or more types of L 1 s and L 2 s, respectively, wherein (a) the polyalkylene oxide has a weight-average molecular weight of 4,000 or more when measured by gel permeation chromatography, by the method described in the present specification, and/or (b) the dispersoid is at least one of nano-carbon, metal nanoparticles, inorganic fibers or organic fibers. L 1 is a straight-chain alkylene group in which at least one hydrogen atom is substituted with Z-Ar, and L 1 may or may not have a substituent other than Z-Ar, L 2 is a straight-chain alkylene group in which at least one hydrogen atom may or may not be substituted with a substituent, there may be one or more Z-Ar's, and when there are a plurality of Z-Ar's, they may be the same or different from each other, Z is a linking group that links L 1 and Ar, and the linking group may or may not contain each of an alkylene chain, an ether bond, an ester bond, and an imide bond, Ar is represented by the following chemical formula,, or; there may be one or more Ar's for one Z; when there are a plurality of Ar's, they may be the same or different from each other; and a naphthyl group in the following chemical formula may be either a 1-naphthyl group or a 2-naphthyl group, R 1, R 2, and R 3 are each a substituent; there may be one or more of each of R 1, R 2, and R 3, or R 1, R 2, and R 3 each may not be present; and when there are a plurality of R 1 s, R 2 s, and R 3 s, R 1 s, R 2 s, and R 3 s may be the same or different from each other, respectively, n and m are each an integer of 1 or more, a sequence of L 1 and L 2 may be any of alternating, random, or block sequences, and there may be one or more types of L 1 s and L 2 s, respectively, R 1, R 2, and R 3 are each a substituent; there may be one or more of each of R 1, R 2, and R 3, or R 1, R 2, and R 3 each may not be present; and when there are a plurality of R 1 s, R 2 s, and R 3 s, R 1 s, R 2 s, and R 3 s may be the same or different from each other, respectively, n and m are each an integer of 1 or more, a sequence of L 1 and L 2 may be any of alternating, random, or block sequences, and there may be one or more types of L 1 s and L 2 s, respectively, wherein (a) the polyalkylene oxide has a weight-average molecular weight of 4,000 or more when measured by gel permeation chromatography, by the method described in the present specification, and/or (b) the dispersoid is at least one of nano-carbon, metal nanoparticles, inorganic fibers or organic fibers.