A spindle apparatus which facilitates assembling and removing operations at the time of maintenance and which is low cost. In the invention, the diameter becomes smaller in the order of an inner peripheral diameter of an outer cylinder (3), an inside diameter of a stator (4), and an outside diameter of a bearing sleeve (11); a sub-assembly (2) made up of a front housing (8), a rotating shaft (6), and the bearing sleeve (11) is withdrawable from the outer cylinder (3); and the diameter of a rotating part in an arbitrary section located rearwardly of the bearing sleeve (11) is made smaller than a minimum diameter of a non-rotating part between a rear end of the bearing sleeve (11) and the section.