An apparatus for monitoring pixel data includes a multiplexer configured to select pixel data applied to at least one of function blocks which is configured to convert the pixel data provided from an external device and adjust characteristics of a display device, a monitoring module configured to store the pixel data selected by the multiplexer, and an analyzing module configured to output a location selection signal to the multiplexer which provides the monitoring module with the pixel data based on the location selection signal, to read out the pixel data stored in the monitoring module by applying a pixel position signal to the monitoring module, and to analyze a variation of the read out pixel data.