Treatment agent for a cosmetic powder containing a reactive organosiloxane represented by the following general formula (1) as a main ingredient: wherein each R 1 is independently an alkyl group having 1 to 30 carbon atoms； each R 2 is independently an alkyl group having 1 to 20 carbon atoms； R 3 is a divalent alkylene group； n is an integer of 1 to 200； and p is an integer of 1 to 3. According to the present invention, there is provided a treatment agent for a cosmetic powder capable of imparting excellent lipophilicity, a cosmetic raw material having cosmetic effect and giving an excellent feeling of use, and a cosmetic.
