1. A speed measurement method using blurred images for detecting the speed of a detected object comprising the following steps: taking a blurred image of the detected object by an image-capturing device; using the blurred image to create a deblurred image and obtain a blur extent; calculating an actual displacement of the detected object by using the blur extent, a focal length of the image-capturing device and a distance between the detected object and the image-capturing device; and calculating the speed of the detected object using the actual displacement of the detected object and a shutter time of the image-capturing device.