Patent ID: 6945536

Claim:
An oil seal provided on an outer circumference of a rotary shaft, the oil seal sealing a first liquid disposed on a first side and a second liquid disposed on a second side, the oil seal comprising: a first seal for sealing the first side of the rotary shaft; a second seal for sealing the second side of the rotary shaft; a sealed space formed by the first seal, the second seal and the rotary shaft; a casing which holds the first seal and the second seal; a sealing section interposed at a position where the first seal and the second seal are held by the casing to form a sealing portion through which a circulation of the first liquid and/or the second liquid is prohibited, the sealing portion extending along the entire circumference of the casing; and a negative-pressure reducer having a communicating portion for operatively fluidly coupling the sealed space with the first side and/or the second side at a position other than the outer circumference of the rotary shaft, the communicating portion of the negative-pressure reducer being covered with the casing.