This inventive thickener or gellant for oil materials is characterized by comprising (A) an high molecular weight organopolysiloxane that has a polyglycerol structure-containing hydrophilic group Q and that is represented by the following structural formula (1): R3-q(R11)qSi—O—(SiR112—O)n1—(SiR11Q-O)n2—(SiR11L-O)n3—Si(R)11)qR3-q wherein R11 is a monovalent hydrocarbyl group or a hydrogen atom； L is a chain organosiloxane group, n1, n2, and n3 are numbers in the ranges 200≦n1≦1000, 0≦n2≦20, and 0≦n3≦50； R is a group selected from L and Q； q is an integer in the range from 0 to 3； wherein when n2=0, q is an integer in the range from 1 to 3 and at least one R is Q. The thickener or gellant exhibits an excellent compatibility with a variety of oil systems.
