A thermally conductive composition comprising: a filler; and a polymer component, wherein the filler comprises at least one surface-treated filler selected from the group consisting of the following filler (A) and filler (B):



Filler (A): A filler surface-treated by a chemical vapor deposition method using a siloxane having one SiH group
Filler (B): A filler surface-treated by a chemical vapor deposition method using a siloxane having two or more SiH groups, wherein at least one group selected from the group consisting of an unsubstituted alkyl group having 6 to 20 carbon atoms, an alkyl group having 2 to 20 carbon atoms having a substituent, and a group having a specific structure is further bonded to a silicon atom on a surface of the filler and introduced.