PURPOSE: To prevent the malfunction in a data recording and reading out of disks having high-density magnetic memory information by fixing a shaft end to a mounting plate without applying stresses on the disk at all.

CONSTITUTION: A stator coil assembly 25 is mounted at a stationary steel shaft 22. A permanent magnet rotator 26 is mounted at a bearing 28 and rotates around the shaft 22 together with a hard disk 30. A head position device 27 has an integral arm 32 carrying a spring type head 34 between the two disks 30. The top end of the shaft 22 is mounted in a stressless state to a mounting plate 52 which is part of a housing 40. The mounting is executed by using a mounting washer 54, applying an adhesive material 66, such as epoxy resin, over the entire part of the relative surfaces of this washer 54 and the spot facing aperture of the mounting plate 52 and engaging and holding the washer 54 and the top end of the steel shaft 22 by means of a core screw 68 made of steel, then curing the epoxy resin 66 thereby fixing the shaft. As a result, the shaft is fixed without the exertion of the stresses thereon at all and, therefore, the shaft is kept free from vibration and the malfunction in data-recording and reading out is prevented.