Provided are surface-treated fine particles which, when added to coatings for the production of films, exhibit excellent reactivity with respect to organosilicon compounds and resins that are matrix components of the coating films, and thereby allow the films to exhibit excellent performance. Oligomer-modified fine particles include inorganic oxide fine particles having a surface modified with an oligomer, the oligomer being derived from a metal alkoxide represented by Formula (1): RnM1(OR′)z-n (1) wherein M1: one or more elements selected from Si, Ti, Zr and Al; R and R′: one or more groups selected from alkyl groups of 1 to 8 carbon atoms, aryl groups and vinyl groups; n: an integer of from 0 to (z−2); and z: the valence of M1. The oligomer has a polymerization degree of 3 or more. The oligomer has a weight average molecular weight in the range of 1000 to 10000.