A fine particle of a silicon polymer having a siloxane group and a silanol group, wherein a moisture adsorption amount of the fine particle at a temperature of 30° C. and a humidity of 80% RH is from 1.0 mg/g to 22.0 mg/g, an amount of the silanol group of the fine particle measured by a titration method using KOH is from 0.012 mmol/g to 0.120 mmol/g, and a number average particle diameter of primary particle of the fine particle is from 0.05 μm to 0.30 μm.