A learning device includes a camera configured to acquire image data by imaging a sample of a product, a physical property information acquisition unit configured to acquire physical property information of the sample, and a processing unit configured to generate a learning model. The processing unit is configured to identify a category of the sample based on rule information relating the physical property information to the category, to generate teacher data by relating the identified category to the image data, and to generate a learning model by machine learning using the teacher data. The learning model outputs the category of the sample in response to an input of the image data of the sample.