A liquid aryl group-containing polyorganosiloxane comprising an arylsiloxy unit represented by RSiO3/2 (wherein R is an aryl group), wherein: the arylsiloxy unit constitutes from 20 to 50 mol % of all the siloxy units constituting the polymer, and an average number of moles of aryl groups per 1 mole of Si atoms in the molecule is within a range of 1.20 to 1.65. A composition with an oil agent of the same, wherein the overall refractive index of the composition is not less than 1.45, and an overall viscosity at 25° C. of the composition is in a range from 100 to 100,000 mPa·s.
