A sealing device configured to be installed to an opening portion between an outer ring and an inner ring of a bearing and inhibits foreign matter in an outer portion of the bearing from entering into an inner portion of the bearing, the sealing device comprising: an attaching ring which is attached to said outer ring; and a seal lip which is retained to said attaching ring and slidably comes into close contact with said inner ring, wherein said seal lip integrally has a first inclined surface portion which is diagonally formed toward an inner side in a diametrical direction and toward an inner side of the bearing from a part of a base end portion of the lip which is towards the inner portion of the bearing, said first inclined surface portion being formed into a shape with a thickness reduced little by little from its base end toward its leading end, and a second inclined surface portion which is diagonally formed toward an inner side in a diametrical direction and toward an outer side of the bearing from the leading end of said first inclined surface portion, said second inclined surface portion being formed into a shape with a thickness approximately constant from its base end toward its leading rend, wherein the leading end of said second inclined surface portion is arranged at the same position in an axial direction as a thickness surface of an inner peripheral end portion of said attaching ring, and the remaining positions of said second inclined surface portion and said first inclined surface portion are arranged further towards the inner side of the bearing than the position in an axial direction of the thickness surface of the inner peripheral end portion of said attaching ring, wherein said second inclined surface portion is set to a sliding portion in relation to said inner ring, and wherein a satin finished processing for enlarging a surface roughness of said sliding portion is applied to said sliding portion. an attaching ring which is attached to said outer ring; and a seal lip which is retained to said attaching ring and slidably comes into close contact with said inner ring, wherein said seal lip integrally has a first inclined surface portion which is diagonally formed toward an inner side in a diametrical direction and toward an inner side of the bearing from a part of a base end portion of the lip which is towards the inner portion of the bearing, said first inclined surface portion being formed into a shape with a thickness reduced little by little from its base end toward its leading end, and a second inclined surface portion which is diagonally formed toward an inner side in a diametrical direction and toward an outer side of the bearing from the leading end of said first inclined surface portion, said second inclined surface portion being formed into a shape with a thickness approximately constant from its base end toward its leading rend, a first inclined surface portion which is diagonally formed toward an inner side in a diametrical direction and toward an inner side of the bearing from a part of a base end portion of the lip which is towards the inner portion of the bearing, said first inclined surface portion being formed into a shape with a thickness reduced little by little from its base end toward its leading end, and a second inclined surface portion which is diagonally formed toward an inner side in a diametrical direction and toward an outer side of the bearing from the leading end of said first inclined surface portion, said second inclined surface portion being formed into a shape with a thickness approximately constant from its base end toward its leading rend, wherein the leading end of said second inclined surface portion is arranged at the same position in an axial direction as a thickness surface of an inner peripheral end portion of said attaching ring, and the remaining positions of said second inclined surface portion and said first inclined surface portion are arranged further towards the inner side of the bearing than the position in an axial direction of the thickness surface of the inner peripheral end portion of said attaching ring, wherein said second inclined surface portion is set to a sliding portion in relation to said inner ring, and wherein a satin finished processing for enlarging a surface roughness of said sliding portion is applied to said sliding portion.