Provided are: an oil-based thickening agent which is capable of providing an oil-based composition that has a high thickening effect on an oil component such as a silicone oil, while achieving excellent feeling of use； an oil-based thickening composition which contains this oil-based thickening agent and a liquid oil component； and a cosmetic preparation in which this oil-based thickening agent or oil-based thickening composition is blended. An oil-based thickening agent which is composed of a silicone-modified polysaccharide compound represented by formula (1) and a silicone emulsifying agent.(In the formula, PL represents a glucose residue of pullulan； R1 represents a monovalent hydrocarbon group having 1-10 carbon atoms； R2 represents a monovalent hydrocarbon group having 1-10 carbon atoms or a siloxy group represented by —OSi(R3)3； R3 represents a monovalent hydrocarbon group having 1-8 carbon atoms； n is an integer of 1-10； a is 0 or 1； and b is 0, 1 or 2. The average number of bonded silicone compounds (substitution degree of silicone compounds) per one constituent sugar unit of the polysaccharide compound is 0.5-2.5； and the average molecular weight of the silicone-modified polysaccharide compound is 50,000-10,000,000.)
