An oil sealing device for preventing a leakage of an oil of a bearing which supports a rotary shaft of a rotating machine has a brush member having a plurality of bristles in contact with the rotary shaft, and an actuator configured to move the brush member in a length direction of the rotary shaft, wherein a sloped surface having different heights along a length direction of the rotary shaft is formed at the rotary shaft, and wherein when the bristles are worn, the actuator moves the brush member in a length direction of the rotary shaft so that the bristles comes into contact with the sloped surface.