The invention provides a speed measuring device and a motor vehicle, wherein the speed measuring device comprises a bearing and a speed sensor. The bearing comprises an inner ring, an outer ring, and a plurality of rolling elements between the inner ring and the outer ring. The speed sensor is an active sensor and is provided with a sensing part which is magnetic. The sensing part of the speed sensor is arranged outside the bearing and is arranged in a radial clearance between the inner ring and the outer ring. The rolling elements are made of soft magnetic material and are used as interference sources for the magnetic field of the sensing part. According to the technical solution of the invention, an encoder is abandoned; and the rolling elements are used as the interference sources for generating an alternating magnetic field, so that simple structure of the speed measuring device is realized and furthermore manufacturing cost and mounting cost are reduced.