When correction values are respectively determined for noise components of “OFFSET COMPONENT OF CCD ELEMENT”, “GRADATION COMPONENT OF BACKGROUND LIGHT” and “OFFSET COMPONENT OF OPTICAL SYSTEM”, the pixel values including as less of these noise components as possible are evaluated. The evaluated pixel values include a noise component of “THERMAL NOISE PLUS READOUT NOISE COMPONENT” which is superposed onto the pixel values. With this taken into consideration, a moving object detection method of an embodiment photographs multiple images of a moving object being an observation object with a photographic area fixed, selects the smallest pixel value in each group of corresponding pixels across the images from image signals representing the images, evaluates image signals including as less of the four noise components as possible by using the smallest pixel value as the correction value for the four noise components.