Disclosed is a spindle device endowed with a sufficient load capacity for bending moment and capable of reducing power loss and heat generation of the main shaft attributable to the radial dynamic pressure bearing. In this spindle device, the rotation of the spindle rotor is supported by a pair of radial dynamic pressure bearing portions, between which there is provided a first cooling chamber so as to circumferentially surround the spindle rotor, atmosphere outside the housing being introduced into the first cooling chamber.