1. A luminance distortion compensating apparatus comprising: an image data receiving circuit configured to receive grayscale image data from a grayscale image displayed on a display panel and to receive full white image data from a full white image displayed on a display panel; and a luminance distortion compensating circuit configured to compensate for a luminance distortion generated by a display panel inspecting apparatus inspecting the display panel, in the grayscale image data, using the grayscale image data and the full white image data.