1. A resolution determination device, comprising: an edge intensity calculation section configured to calculate an edge intensity for each of a plurality of pixels included in an input image based on a difference between the luminance of the pixel and the luminance of a pixel adjoining the pixel; and a resolution determination section, wherein the resolution determination section includes a coring processing section configured to bring the edge intensity near to value 0 when the edge intensity is determined to be noise, an edge change point detection section configured to detect a pixel at which the adjoining edge intensities are different in sign, a first accumulation section configured to accumulate results of the edge change point detection section for a plurality of pixels, and a second accumulation section configured to accumulate pixels of which the accumulation value exceeds a parameter value input from outside the resolution determination section for one frame, and the resolution determination section determines whether or not the input image is an image obtained by up-converting an image having a resolution equal to or less than a predetermined value, and whether or not the input value is a flat image, based on the accumulation result, and outputs the determination result.