1. A target travel direction detecting method comprising: an image acquiring step of acquiring an image including a target picked up at predetermined time intervals; an extracted image creating step of creating an image including an arbitrary component extracted from the image; a target position detecting step of causing a matrix template to scan the extracted image at time t to detect the position of the target; a pixel value storing step of storing each pixel value of the extracted image at time t into the template; a value-matching pixel detecting step of causing a template storing the pixel value to scan the extracted image at time t+1 to detect the position of a pixel whose value matches a pixel value of the template; and a travel-direction-extracted image creating step of plotting a pixel value set to accordance with the travel direction of the target at the same coordinate position as the pixel position detected in the value-matching pixel detecting step to create a travel-direction-extracted image.