A gate insulation film composed of a polymer compound containing at least one repeating unit selected from the group consisting of a repeating unit of formula (2) and a repeating unit of formula (3); a repeating unit of formula (4) and a repeating unit of formula (1), or composed of a composition containing the polymer compound, wherein the molar ratio of the repeating unit of formula (4) to the sum of the repeating unit of formula (2) and the repeating unit of formula (3) is 50/100 to 200/100 with the total charging amount (molar quantity) of the repeating unit of formula (2) and the repeating unit of formula (3) being 100 and the content of the repeating unit of the following formula (1) is 75% by mol or more with the total content of all repeating units in the polymer compound being 100% by mol.