1. An image correction device comprising: a memory storing instructions; and at least one processor configured to process the instructions to implement: a reference brightness correction parameter calculation unit configured to calculate, in a reference image in which a reference object moving in a space that is an image capturing target is captured, a reference brightness correction parameter based on brightness information relating to an area of the reference object and coordinate information specifying a position of the area, and a correction unit configured to correct a captured image in which the space is captured and a correction-target object is captured, based on the reference brightness correction parameter, wherein the reference brightness correction parameter calculation unit is further configured to calculate a ratio between an average brightness value relating to an area of the reference object in one reference image, and an average brightness value relating to an area of the reference object in another reference image, as the reference brightness correction parameter which is to be associated with coordinate information specifying the position of the reference object in the another reference image.