A method for inspecting a display device includes preparing a target substrate comprising sub-pixels in which light-emitting elements are disposed, dividing each of first regions of the sub-pixels into second regions, obtaining a gray value of each of the second regions, generating a random number using the gray value, calculating a representative value of each of the first regions by reflecting variables in the random number, and summing the representative values of the first regions to calculate a number of light-emitting elements of the sub-pixels.