NOVELTY - An addition curable silicone composition contains (in parts mass) organopolysiloxane (A) (100), organopolysiloxane (B) (1-100), organosilicon compound and platinum group metal-type catalyst. The organopolysiloxane (A) has 2 or more silicon atomic union aliphatic unsaturated group and one or more silicon atomic union perfluoroalkyl group in one molecule. The organopolysiloxane (B) has 2 or more silicon atomic union aliphatic unsaturated group and one or more silicon atomic union perfluoroalkyl group in one molecule, and branched structure of siloxane unit (I) and/or (II).    USE - Addition curable silicone composition for optical element (claimed) e.g. light emitting diode. Uses include but are not limited to photodiode, phototransistor, solar cell, charge coupled device, etc.    ADVANTAGE - The additional curable silicone composition provides hardened material with high transparency, strength and light extraction efficiency, and low refractive index.    DETAILED DESCRIPTION - An addition curable silicone composition contains (in parts mass) organopolysiloxane (A) (100), organopolysiloxane (B) (1-100), organosilicon compound and platinum group metal-type catalyst. The organopolysiloxane (A) is linear compound having 2 or more silicon atomic union aliphatic unsaturated group and one or more silicon atomic union CF3-(CF2)m-(CH2)n- group in one molecule. The organopolysiloxane (B) has 2 or more silicon atomic union aliphatic unsaturated group and one or more silicon atomic union CF3-(CF2)m-(CH2)n- group in one molecule, and branched structure of siloxane unit of formula: SiO4/2 (I) and/or RSiO3/2 (II). The organosilicon compound has 2 or more silicon atom-bonded hydrogen atoms in one molecule. The ratio of silicon-hydrogen group of organosilicon compound with respect to total aliphatic unsaturated group of organopolysiloxane (A,B) is 0.2-5.    m=0 or more;    n=1 or more;and    R=optionally substituted monovalent hydrocarbyl.    An INDEPENDENT CLAIM is included for optical element, which is obtained by sealing hardened material of the silicone composition.