An image processing system includes: an object detecting unit that detects a moving body object from image data of an image of a predetermined area; an object-occurrence-position detecting unit that detects an occurrence position of the object detected by the object detecting unit; and a valid-object determining unit that determines that the object detected by the object detecting unit is a valid object when the object is present in a mask area set as a non-detection target in the image of the predetermined area and the occurrence position of the object in the mask area detected by the object-occurrence-position detecting unit is outside the mask area.