To provide a bearing device capable of stably performing pre-load management even if grease intrudes into a bearing that supports a pinion shaft of a differential gear device.

The bearing device includes: the bearing 30 having an outer ring 32 having an outer ring raceway surface formed on an inner peripheral surface, an inner ring 31 having an inner ring raceway surface formed on an outer peripheral surface, a plurality of rolling elements 33 capable of rolling between the outer ring raceway surface and the inner ring raceway surface in the circumferential direction, and a cage 34 for holding the plurality of rolling elements at prescribed intervals; a housing 10; a shaft body 20 rotatably supported to the housing by the bearing; a pre-load nut 40 for applying a pre-load to the bearing by being screwed with the shaft body; a spacer 50 disposed between the inner ring of the bearing and the pre-load nut; and an oil seal 60 provided at the outer diameter side of the spacer for sealing a space between the housing and the spacer. The viscosity of the grease coated on the oil seal and the viscosity of rust-preventive oil coated on the bearing are almost the same at a temperature at pre-loading work.