To provide a bearing device capable of finding a preload applied to a bearing without making an electrode into contact with a rotor, reducing manufacturing costs, and elongating a life of device parts.

When thickness of a lubricating oil film changes according to a load applied to bearings 3A, 3B and a value of a preload changes, an electrostatic capacity of each capacitor corresponding part changes according to the change of the oil film thickness. Therefore, the bearing preload is detected from a value measured by electrostatic capacity measuring means 9.