The utility model discloses a bearing rotating speed measuring device, which comprises a magnetoelectric rotating speed sensor, a first-stage sleeve, a second-stage sleeve and a gear, and is characterized in that the gear is sleeved on the first-stage sleeve; a plurality of first threaded holes penetrating through the pipe wall are formed in the pipe wall of the first-stage sleeve, a first grooveis formed in the inner wall of the first-stage sleeve, and the first groove is parallel to the length direction of the first-stage sleeve; the second-stage sleeve is used for being arranged in the first-stage sleeve in a sleeved mode. Therefore, the bearing needing speed measurement can be matched and adapted. A second protrusion matched with the first groove in the inner wall of the first-stage sleeve is arranged on the outer wall of the second-stage sleeve, a second threaded hole corresponding to the first threaded hole is further formed in the second-stage sleeve, and a combination of the first-stage sleeve and the second-stage sleeve is connected to the bearing in a sleeving mode through a bolt to be matched with the magneto-electric rotating speed sensor for rotating speed measurement. The rotating speed measuring device provided by the utility model can conveniently measure the rotating speeds of bearings with different diameters, and meanwhile, the device is more convenient andfaster to disassemble and assemble.