The present invention provides a copolymer which can be used as an oily gelling agents for preparing a stable oily gel composition. The copolymer according to the present invention is characterized by containing a hydrophobic monomer represented by the following formula (1), and a hydrophilic monomer represented by the following formula (2) and/or the following formula (3). in formula (1), R1 represents a straight or branched alkyl group having a carbon number of 16 to 22. R2 represents a hydrogen atom or a methyl group. in formula (2), R3 represents a hydrogen atom, a glyceryl group, a hydroxyalkyl group having a carbon number of 1 to 4, or a polypropylene glycol group represented by -(C3H6O)nH (n is an integer of 2 to 10), R4 represents a hydrogen atom or a methyl group. in formula (3), R5 represents a hydrogen atom or a methyl group, R6 represents a straight or branched alkyl or hydroxyalkyl group having a carbon number of 1 to 4 or a substituent represented by the following formula (4) 本發明是提供可做為油性膠化劑用之共聚合物，而該油性膠化劑係可用於調製安定的油性膠狀組成物。本發明的共聚合物的特徵是含有下述通式(1)表示的疏水性單體，及下述通式(2)及/或下述通式(3)表示的親水性單體。(式(1)中，R1是直鏈或支鏈的具有16至22個碳原子的烷基。R2是氫原子或甲基)(式(2)中，R3是氫原子、甘油基、直鏈或支鏈的具有1至4個碳原子的羥烷基，或-(C3H6O)nH表示的聚丙二醇基(但n是2至10的整數)。R4是氫原子或甲基)(式(3)中，R5是氫原子或甲基。R6是直鏈或支鏈的具有1至4個碳原子的烷基或羥烷基，或下述通式(4)表示的取代基)
