A silicone-based copolymer resin powder, prepared by reacting a siloxane oligomer obtained from ring-opening of (a1) a cyclic organosiloxane in the presence of (a3) an acid catalyst and (a4) an anionic surfactant with (a2) a silane coupling agent having an alkoxy group and a polymerizable double bond to obtain (A) a linear or branched organopolysiloxane containing at least 2 silicon-bonded hydroxyl groups per molecule,copolymerizing (A) the linear or branched organopolysiloxane with (B) an ethylenically unsaturated monocarboxylic acid ester monomer to form a copolymer as a core, andfurther polymerizing to the copolymer another ethylenically unsaturated monomer as a shell,the powder containing up to 0.3% by weight of the cyclic organosiloxane and up to 1% by weight of the anionic surfactant.
