A mobile entity detection apparatus 10 includes: a feature point extraction unit 11 configured to extract, from image data output by an imaging device of a vehicle, a feature point moving in an image; an optical flow specification unit 12 configured to compare the latest image data with image data that was output in the past, and specify an optical flow for each feature point; a clustering unit 13 configured to perform clustering on the optical flow based on the optical flow and the position of the optical flow in the image, and separate the optical flow into a cluster; a filtering unit 14 configured to remove a cluster that corresponds to an object forming a background from among the clusters based on the traveling direction and speed of the vehicle; and a mobile entity specification unit 15 configured to specify a mobile entity in the image using a result of clustering after cluster removal.