A defect inspection device includes at least one memory storing instructions and at least one processor. The at least one processor is configured to execute the instructions to acquire a first image of an inspection target created in a first creation method, acquire a second image obtained by photographing the inspection target, extract index data similar to the acquired first image with reference to a database, the index data being a third image created in the first creation method or a feature quantity obtained by the third image, the database including the index data associated with correct data that is used as a comparison target of the index data and is an image determined not to be defective in previous inspection, acquire the correct data associated with the extracted index data in the database, generate a reference image on the basis of the acquired correct data, and estimate a pixel associated with a defective position on the inspection target photographed in the second image by comparing the reference image with the second image.