Provided is a surface treatment powder which is hydrophobic when the powder is at dry state and is hydrophilic when the powder is contacted with water, and thus the powder has both properties of holding makeup for a long time and easily washing out.The powder surface of the surface treatment powder of the present invention is covered with a first block copolymer represented by the following formula (1).(wherein, R1 and R2 each independently represents an alkyl group, a polyoxyalkylene group, an acyl group, a phenyl group, an aralkyl group, X represents a C1-18 alkyl chain which may form an ether with a non-adjacent carbon substituted by an oxygen, Z1 represents hydrogen or methyl group, n and m represent a degree of polymerization.)本發明之課題在於提供一種表面處理粉體,其係藉由於乾燥時為疏水性,而在與水接觸時變為親水性,從而兼顧化妝保持性與洗除性。該課題之解決手段為一種粉體表面被覆有下述通式(1)表示的第1嵌段共聚物的表面處理粉體,(式(1)中,R1、R2分別獨立地表示烷基、聚氧伸烷基、醯基、苯基、芳烷基,X表示無鄰接的碳原子可經氧原子取代從而形成醚的碳數1至18的烷鏈,Y表示單鍵或2價的連接基,Z1表示氫原子或甲基,n、m表示聚合度)。1‧‧‧Q片段2‧‧‧PTMC片段
