1. A three-dimensional object detection device, comprising: an image capture means that captures an image of a predetermined area; an image conversion means that performs a view point conversion on the image obtained by the image capture means into a birds-eye view image; a brightness detection means that detects a brightness in the predetermined area; a first three-dimensional object detection means that detects a three-dimensional object by generating differential waveform information from a differential image of the bird's-eye view images obtained by the image conversion means at different times and by confirming that the differential waveform information is equal to or greater than a first threshold a when the brightness detected by the brightness detection means is equal to or greater than a predetermined value; and a second three-dimensional object detection means that detects a three-dimensional object by detecting edge information from the bird's-eye view image obtained by the image conversion means and confirming that the edge information is equal to or greater than a second threshold β when the brightness detected by the brightness detection means is less than the predetermined value the detects a three-dimensional object on the basis of the edge information.