Abstract: Provided is a carboxylic acid co-modified organopolysiloxane that can stably and uniformly disperse various hydrophobic powders in an aqueous phase and has excellent functionality as a powder dispersant or the like. Compositions, such as topical agent compositions comprising the carboxylic acid co-modified organopolysiloxane, are also provided. The carboxylic acid co-modified organopolysiloxane is expressed by the following structural formula (1): where R1 is a C6 or lower hydrocarbon group or a hydrogen atom, R2 is a C6-30 monovalent hydrocarbon group, L1 is a specific organosilicon-containing organic group, Rc is a carboxyl group-containing organic group, R? is a group independently selected from the aforementioned R1, R2, L1 and Rc, but Rc and L1 are always included in the molecule.