1. A flash band determination device that determines whether or not a flash band caused by an external flash of light is present in an image obtained through image pickup, comprising: at least one processor; a memory; wherein the at least one processor is configured to function as following units by processing data stored in the memory, a first determination unit configured to determine whether or not a high-luminance area, which is an area having a luminance level exceeding a predetermined luminance level, is present in the image; and a second determination unit configured to determine, in a case where it is determined by said first determination unit that the high-luminance area is present when determining whether or not a flash band which is an area having a luminance level higher than a predetermined threshold level is present in a difference image which is a difference between two images which are continuously obtained, whether or not the flash band is present, by excluding an area corresponding to the high-luminance area, as a determination excluded area, from the difference image.