A printing apparatus includes (A) a head that discharges first ink and second ink having a color different from that of the first ink, (B) an optical sensor that includes a light source and a light receiving section, and (C) a controller. In the printing apparatus, when the controller corrects a discharge amount of the second ink, the controller causes the head to discharge the first ink to form a first pattern on a medium, causes the optical sensor to detect light reflected from the first pattern, causes the head to discharge the second ink to form a plurality of second patterns having different gradation values on the first pattern, and causes the optical sensor to detect light reflected from the second pattern.