A defect detecting method of a display device includes a defect counting process that measuring a feature amount for each partial region of a display device (P32), and counting regions which is determined as a defective portion based on the measured feature amount of the region (P36), a process that stopping a manufacturing line of the display device when a number of defects counted at the defect counting process is greater than a first threshold value (P38, P42), a defect density calculating process that calculating a defect density in a predetermined area when the number of defects counted at the defect counting process is smaller than the first threshold value (P38), and a process that stopping the manufacturing line of the display device when the defect density calculated at the defect density calculating process is higher than a second threshold value (P40, P42).