This paper investigates the availability of aerostatic journal bearings to a high vacuum chamber, theoretically and experimentally. This bearing has several steps of a viscous seal, and vacuum pumps are connected to the space between viscous seals in order to achieve the vacuum degree of less than 10^-3 Pa in a vacuum chamber. The vacuum degree of a chamber is affected by many design parameters such as the number of steps of a viscous seal, seal length, seal gap, the pumping speed of vacuum pumps and the conductance of exhaust tubes. Influences of these design parameters on the vacuum degree are theoretically discussed and the theoretical predictions are compared with the experimental data. It is found that the aero-static journal bearing with viscous seals can achieve the vacuum degree of the order of 10^-4 Pa in a vacuum chamber by properly designing the seal regions.