NOVELTY - A curable composition (C1) comprises a) silica fine particles; b) polymerizable compound comprising at least one compound selected from (meth) acrylate compound (b1) having at least one ethylenically unsaturated group and having aromatic ring structure, and (meth) allyl compound (b2) having at least one ethylenically unsaturated group and having aromatic ring structure; and c) polymerization initiator. The particles (a) are obtainable by subjecting silica fine particles (a1) to a surface treatment with a surface treatment agent containing a silane compound (d) and a silane compound (e).    USE - As curable composition for preparing cured material for making optical material or electronic materials (claimed) such as transparent plates, optical lenses, optical disk substrates, plastic substrates for liquid crystal display elements, substrates for color filters, substrates for organic EL display elements, substrates for solar cells, touch panels, optical elements, sealing media of optical waveguide and LED.    ADVANTAGE - The composition has low viscosity and excellent handling properties and also excellent stability during storage. The cured material has excellent transparency, and thermal durability, and high surface hardness, and a small Abbe number i.e. Abbe number of less than or equal to 50.    DETAILED DESCRIPTION - A curable composition (C1) comprises a) silica fine particles; b) polymerizable compound comprising at least one compound selected from (meth) acrylate compound (b1) having at least one ethylenically unsaturated group and having aromatic ring structure, and (meth) allyl compound (b2) having at least one ethylenically unsaturated group and having aromatic ring structure; and c) polymerization initiator. The silica fine particles (a) are obtainable by subjecting silica fine particles (a1) to a surface treatment with a surface treatment agent containing a silane compound (d) having formula H2C=C(R1)-C(=O)-O-(CH2)a-Si(R2)b(R3)c(OR4)3-b-c (I) and a silane compound (e) of formula (X-(CH2)d)e-Si(R5)f(R6)g(OR7)4-e-f-g (II).    R1=H or methyl;    R2=1-12C alkyl or a phenyl group;    R3=halo;    R4=H or 1-10C hydrocarbon;    a=8-17;    b=0-2;    c=0-3;or    b+c=0-3;    X=an organic group having an aromatic ring structure with 6-12 carbon atoms;    R5=R2;    R6=R3;    R7=R4;    d=0-6;    e=1-3;    f=0-2;    g=0-3;or    e+f+g=1-4;or    e+f=1-3.    When the total of b and c is 0 or 1, then R4 are same or different; and when the total of e, f and g is 1 or 2, then R7 are same or different. INDEPENDENT CLAIMS are included for the following:    (1) a cured material obtainable by curing the curable composition (C1); and    (2) an optical material or electronic material comprising the cured material.