A noise measurement device for measuring noise of a test image displayed on a display device including a display panel and an input sensor configured to sense an external input, includes a luminance meter, a converter, and a determiner. The luminance meter is configured to: measure a luminance of the test image in a state in which the input sensor is turned on to generate first luminance measurement values; and measure a luminance of the test image in a state in which the input sensor is turned off to generate second luminance measurement values. The converter is configured to apply a contrast sensitivity function to luminance difference values between the first and second luminance measurement values to generate final conversion values. The determiner is configured to compare the final conversion values with a predetermined reference range to determine whether a defect exists in the test image.