A method for producing an amorphous oxide thin film includes: a pre-treatment process of selectively changing a binding state of an organic component, at a temperature lower than a pyrolysis temperature of the organic component, in a first oxide precursor film containing the organic component and In, to obtain a second oxide precursor film in which, when an infrared wave number range of from 1380 cm−1 to 1520 cm−1 in an infrared absorption spectrum obtained by performing a measurement by Fourier transform infrared spectroscopy is divided into an infrared wave number range of from 1380 cm−1 to 1450 cm−1 and an infrared wave number range of from more than 1450 cm−1 to 1520 cm−1, a peak positioned within the infrared wave number range of from 1380 cm−1 to 1450 cm−1 exhibits the maximum value in the infrared absorption spectrum within an infrared wave number range of from 1350 cm−1 to 1750 cm−1; and a post-treatment process of removing the organic component remaining in the second oxide precursor film, to transform the second oxide precursor film into an amorphous oxide thin film containing In.