The subject of the present invention is to provide an organic thin film transistor with a small hysteresis. The means for solving the subject is a resin composition for an organic thin film transistor gate insulating layer comprising (A) a macromolecule that comprises at least one repeating unit selected from the group consisting of repeating units represented by Formula (1), repeating units represented by Formula (1′), and repeating units represented by Formula (2) and contains two or more first functional groups in its molecule, wherein the first functional group is a functional group that generates, by the action of electromagnetic waves or heat, a second functional group that reacts with active hydrogen, and (B) at least one compound selected from the group consisting of low-molecular compounds containing two or more active hydrogens in each molecule and macromolecules containing two or more active hydrogens in each molecule.