1. A moving body detecting device comprising a processing circuitry: the processing circuitry is configured to: acquire motion information on an imaging sensor capable of performing imaging with a first exposure time and a second exposure time longer than the first exposure time, the motion information comprising a posture of the imaging sensor; generate an approximate image generated by approximating one of a first photographic image imaged with the first exposure time and a second photographic image imaged with the second exposure time to another photographic image, on the basis of the motion information; generate a blurry image by performing image processing on the first photographic image on the basis of the motion information; and detect a moving body captured in the first and second photographic images, on the basis of the approximate image and the another photographic image, wherein the moving body is detected as a difference between the blurry image and the second photographic image.