A moving body detecting device in accordance with embodiments includes a motion information acquirer, approximate image generator, and moving body detector. The motion information acquirer generates motion information on an imaging device capable of performing imaging with a first exposure time and a second exposure time longer than the first exposure time. The approximate image generator generates 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. The moving body detecting device detects a moving body captured in the first and second photographic images, on the basis of the approximate image and the other photographic image.