A machine learning method includes: obtaining a discharge parameter on discharging performed by a liquid discharge head discharging liquid; obtaining an image quality determination result produced by determining a printed image quality; and learning the relationship between the discharge parameter and the image quality determination result. Also, the discharge parameter desirably includes a discharge state value indicating a discharge state of the liquid discharge head and a discharge result value indicating a discharge result of the liquid discharged on a print medium from the liquid discharge head. The machine learning method includes learning the relationship between the discharge state value and the discharge result value, and the image quality determination result.