An oblique contact ball bearing adopted to support a pinion shaft, where a sufficient range of rotation torque is provided for the oblique contact ball bearing to facilitate highly accurate setting, adjustment, and management of preload. To achieve the above, in the oblique contact ball bearing, a rust preventive oil (35) having kinematic viscosity at 20°C of 1 - 30 mm /s is provided at the portions where raceways (11a, 11b, 13a, 13b) of inner and outer rings (11, 13) and balls (17, 18) are in contact with each other. This increases rotation torque of the bearing and preload setting is made in this state. As a result, when a predetermined pressure-contact force (thrust load) is applied to the balls (17, 18) and to the raceways (11a, 11b, 13a, 13b), an oil-less state is relatively easily obtained and only an oil amount necessary for rust prevention stays on the raceways (11a, 11b, 13a, 13b) etc.