Abstract: A siloxane polymer contains a silsesquioxane unit and a linear siloxane unit in its main chain and has a cage-type silsesquioxane structure in its side chain. A highly transparent and flexible film having a small linear thermal expansion coefficient is produced by utilizing the cohesion force (physical crosslinking) of the cage-type silsesquioxane in the side chain. The siloxane polymer has repeating units respectively represented by formulae (1) and (4), and has terminal groups respectively represented by formulae (5L) and (5R) at its right and left terminals, wherein A represents a structure shown below.

Abstract: A condensation-curable resin composition which contains: (A) an organosilicon compound containing a structural unit (i) represented by the following formula (i) and a structural unit (ii) represented by the following formula (ii), having a SiOH group at both ends of the molecular chain, and having a weight average molecular weight of 10,000 or more and 10,000,000 or less; and (B) an organometallic compound having three or more condensation-reactive groups. In formula (i), each R1 is independently a hydrocarbon group having 1 to 8 carbon atoms. In formula (ii), each R2 is independently a hydrocarbon group having 1 to 8 carbon atoms.