Provided are a polyalkylsilsesquioxane fine particle having hydrophobicity and having a small particle diameter, an external additive for toner and a dry toner for electrophotography each using the same, and a method of manufacturing a hydrophobized spherical polyalkylsilsesquioxane fine particle. The hydrophobized spherical polyalkylsilsesquioxane fine particle has a mass-based median diameter in a centrifugal sedimentation method within the range of from 0.05 µm to 0.3 ¼m. The fine particle is produced through, for example, at least a process involving: mixing a raw material solution prepared using an alkyltrialkoxysilane with an alkaline aqueous medium to obtain a polycondensation reaction liquid; mixing the polycondensation reaction liquid with an aqueous solution to obtain a fine particle dispersion liquid; and blending a hydrophobizing agent in the fine particle dispersion liquid.
