Bearing device

A bearing device mountable on a smaller bearing and allowing to be automatically lubricated for a long period, comprising an inner ring 2 and an outer ring 1 rotated relative to each other, cages and rolling elements 3 held by the cages which are disposed in an annular space between the inner and outer rings, a seal ring 5 disposed on both sides of the inner and outer rings, and a unit body 7 formed of a battery 6, a tank 8 for storing lubricant, and a pump 10 sucking and discharging the lubricant from the tank 8 which is disposed between the outer ring 1 and the inner ring 2 detachably from the seal ring 5, wherein the lubricant is discharged from the pump 10 into the annular space in which the rolling elements 3 are disposed and the discharged amount of the lubricant from the pump is controlled by a sensor and a control circuit, and the unit body 7 is formed detachable, whereby a lubrication unit installed in the bearing can be made compact and slim.