Document classification device and trained model

A method, implemented by circuitry of a document classification device that generates a document classification model which is a model for classifying a document and which outputs identification information for identifying a result of classification on the basis of an input document by machine learning, the method comprising:

• acquiring learning data including a document and the identification information correlated with the document;
• extracting words included in the document and character information which is a character string including one character of characters constituting the words or a plurality of characters consecutive in the words and which is one or more pieces of information capable of being extracted from the words as features;
• and
• performing machine learning on the basis of the feature extracted from the document and the identification information correlated with the document and to generate the document classification model,
• wherein the method includes extracting the character information from a word satisfying a predetermined condition out of the words included in the document,
• wherein the circuitry extracts the character information from a word corresponding to a first part of speech out of the words included in the document.