An object of the present invention is to provide a polymer obtained from novel monomers, a composition containing the polymer, an electronic material composition, and an electronic element, the polymer, by being added to the electronic material composition or ink applied for coating film formation, improving the smoothness (leveling property) of a coating film to be obtained without deteriorating a driving stability of the electronic element. With the novel siloxane monomers, the polymer thereof, the composition containing the polymer, and the electronic material composition according to the present invention, it is possible to produce a smooth organic thin film. The electronic element including either of these compositions has a prolonged element lifetime and improved driving stability.