A novel organopolysiloxane copolymer is disclosed. The copolymer has excellent surface active power and exhibits excellent blending stability in cosmetic preparations and excellent feeling improvement characteristics in comparison to conventionally known polyether-modified silicones and silicone-containing alternating copolymers. The organopolysiloxane copolymer can be used in combination with various cosmetic formulation ingredients. The copolymer is an AB-type organopolysiloxane copolymer which has a silylalkyl group having a carbosiloxane dendrimer structure at one end of the molecular chain, and a hydrophilic segment at the other end. A method for producing the AB-type organopolysiloxane copolymer; a surfactant and a powder processing agent which are respectively composed of the organopolysiloxane copolymer; and a composition for external application and a cosmetic formulation which respectively contain the organopolysiloxane copolymer are also disclosed.