A processing method includes acquiring first parallel text data which is a pair of a first text described in a first language and a first translation of the first text into a second language; evaluating whether the first parallel text data has a possibility of mistranslation on the basis of words included in the first text and the first translation; and outputting information based on the evaluation result. It is evaluated whether the first parallel text data has a possibility of mistranslation on the basis of results of (1) a first determination as to whether the first text includes either or both of a word with a first meaning and an antonym of the word and (2) a second determination as to whether the first translation includes either or both of a translation word with the first meaning and an antonym of the translation word.