1. An abnormal image detection device that detects whether or not at least one of a plurality of original images is abnormal, the plurality of original images being obtained from an image pickup detector and used to prepare a parallax image, the parallax image having a plurality of pixels, the abnormal image detection device comprising: a reliability determination part that determines whether or not each of the pixels of the parallax image has a low reliability, the reliability determination part having an edge intensity determination section that for each respective pixel of the original images, determines whether or not the edge intensity of the respective pixel is smaller than or equal to a threshold value, and if the edge intensity of the respective pixel is smaller than or equal to the threshold value, determines that one of the pixels in the parallax image, which corresponds to the respective pixel, has the low reliability; a computation part that computes a total number of pixels which each has the low reliability as determined by the reliability determination part; and an abnormality determination part that determines that the parallax image is abnormal, when the total number of pixels computed by the computation part exceeds a predetermined value.