An object of the present invention is to provide a composition for forming an organic semiconductor film that makes it possible to obtain an organic semiconductor film having excellent mobility and uniformity thereof, an organic semiconductor element including an organic semiconductor film having excellent mobility and uniformity thereof, and a method for manufacturing the organic semiconductor element.The composition for forming an organic semiconductor film of the present invention contains an organic semiconductor as a component A and a polymer chemically modified some or all of the ethylenically unsaturated double bonds of a ethylenically unsaturated double bond-containing polymer, as a component B. It is preferable that the ethylenically unsaturated double bond-containing polymer is at least one kind of polymer selected from the group consisting of natural rubber, an acrylonitrile-butadiene copolymer, polyisoprene, a styrene-butadiene copolymer, polybutadiene, polychloroprene, an ethylene-propylene-diene copolymer, a styrene-butadiene-styrene block copolymer, and a styrene-isoprene-styrene block copolymer.