A material of cured film, a thermosetting film and a display device are provided. The thermosetting composition includes a solvent and at least one siloxane polymer selected from the group consisting of siloxane polymer (A) obtained by hydrolyzing or condensing a silane mixture containing a monofunctional silane represented by formula (1) and a trifunctional silane represented by formula (2), and siloxane polymer (B) obtained by hydrolyzing or condensing a silane mixture containing a bifunctional silane represented by formula (3) and a tetrafunctional silane represented by formula (4). R independently represents hydrogen, an alkyl group having 1 to 10 carbons whose arbitrary hydrogen can be replaced by a halogen, an aryl group having 6 to 10 carbons whose arbitrary hydrogen can be replaced by a halogen, or an alkenyl group having 2 to 10 carbons whose arbitrary hydrogen can be replaced by a halogen. R′ independently represents a hydrolyzable group.