A motor bearing system comprising: a rolling bearing that supports a rotary shaft of a motor; a slide bearing that is arranged in parallel with the rolling bearing on an axis of the rotary shaft to support the rotary shaft, the slide bearing being operable as a gas-lubricated bearing that achieves gaseous lubrication with gas supplied to the slide bearing; a pump that supplies the gas to the slide bearing; characterized in that the motor bearing system further comprises a detector that detects a rotation speed of the motor; and a controller that controls the pump on the basis of the rotation speed detected by the detector, wherein the controller controls the pump such that, when the rotation speed is equal to or higher than a first speed and is lower than a second speed that is higher than the first speed, the rolling bearing does not function as a bearing that supports the rotary shaft, but the slide bearing functions as the bearing that supports the rotary shaft, and the slide bearing functions as the gas-lubricated bearing, and controls the pump to stop the pump or reduce a driving force of the pump to be smaller than that at the time when the rotation speed is equal to or higher than the first speed and lower than the second speed in the case where the rotation speed is equal to or higher than the second speed and a radial load exerted on the rotary shaft is smaller than a predetermined value, and the controller further controls the pump such that, in the case where the rotation speed is equal to or higher than the second speed and the radial load exerted on the rotary shaft is equal to or larger than the predetermined value, the pump is not stopped, and the driving force of the pump is increased to be larger than that at the time when the radial load is smaller than the predetermined value. a rolling bearing that supports a rotary shaft of a motor; a slide bearing that is arranged in parallel with the rolling bearing on an axis of the rotary shaft to support the rotary shaft, the slide bearing being operable as a gas-lubricated bearing that achieves gaseous lubrication with gas supplied to the slide bearing; a pump that supplies the gas to the slide bearing; characterized in that the motor bearing system further comprises a detector that detects a rotation speed of the motor; and a controller that controls the pump on the basis of the rotation speed detected by the detector, wherein the controller controls the pump such that, when the rotation speed is equal to or higher than a first speed and is lower than a second speed that is higher than the first speed, the rolling bearing does not function as a bearing that supports the rotary shaft, but the slide bearing functions as the bearing that supports the rotary shaft, and the slide bearing functions as the gas-lubricated bearing, and controls the pump to stop the pump or reduce a driving force of the pump to be smaller than that at the time when the rotation speed is equal to or higher than the first speed and lower than the second speed in the case where the rotation speed is equal to or higher than the second speed and a radial load exerted on the rotary shaft is smaller than a predetermined value, and controls the pump such that, when the rotation speed is equal to or higher than a first speed and is lower than a second speed that is higher than the first speed, the rolling bearing does not function as a bearing that supports the rotary shaft, but the slide bearing functions as the bearing that supports the rotary shaft, and the slide bearing functions as the gas-lubricated bearing, and controls the pump to stop the pump or reduce a driving force of the pump to be smaller than that at the time when the rotation speed is equal to or higher than the first speed and lower than the second speed in the case where the rotation speed is equal to or higher than the second speed and a radial load exerted on the rotary shaft is smaller than a predetermined value, and the controller further controls the pump such that, in the case where the rotation speed is equal to or higher than the second speed and the radial load exerted on the rotary shaft is equal to or larger than the predetermined value, the pump is not stopped, and the driving force of the pump is increased to be larger than that at the time when the radial load is smaller than the predetermined value.