<p>A magnetic disc unit which can restrain occurrence of flutter so as to countermeasure such a problem that the larger the rotational speed of discs, the higher the flutter, causing heat positioning errors, in order that the high rotational speed and high positioning accuracy are consistent with each other. Discs (1) are surrounded along their outer peripheries by a shroud (outer wall) (20) while a gap between end faces of the discs (1) and the shroud (20) is decreased to a predetermined distance, thereby to eliminate air pressure differential between opposite surfaces of each of the discs in order to reduce flutter. <IMAGE></p>