In the power steering systems used for automobiles, because of its small size and low noise, a balanced type hydraulic vane pump is mainly used as a power source. Therefore it is requested to research on the lubrication characteristics of a oil hydraulic vane pump which is the key part to improve its performance. The performance of a oil hydraulic vane pump is influenced by the lubrication characteristics of the critical sliding components. Thus, lubrication characteristics between the shaft and the journal bearing have to be researched for the design and the performance improvement of a oil hydraulic vane pump. Therefore, in this paper, it is theoretically investigated that the lubrication characteristics between the shaft and the journal bearing of a balanced type oil hydraulic vane pump for power steering systems. The results demonstrate that lubrication characteristics are significantly influenced by the clearance between the shaft and the journal bearing.