Sealing device

A sealing device which is mounted in an recessed part having an annular shape and formed on an inner peripheral surface of a cylinder or on an outer peripheral surface of a piston which moves on the inner peripheral surface of the cylinder along an axial direction, the recessed part having a predetermined depth in a radial direction orthogonal to the axial direction, the sealing device comprising:

• a sealing member having an annular shape and having a sliding surface which slidably contacts with the inner peripheral surface of the cylinder or with the outer peripheral surface of the piston;
• and
• a ring member having an annular shape and made of an elastic material which presses the sealing member toward the inner peripheral surface of the cylinder or toward the outer peripheral surface of the piston, wherein
• the sealing member has a groove and a slit, the groove being formed to have an annular shape in a circumferential direction along the sliding surface, and the slit being formed so as to allow communication from a side surface of the sealing member to the groove, and
• the sealing member includes a contamination sealing portion which functions as a contamination seal and a hydraulic sealing portion which functions as a hydraulic seal, the contamination sealing portion being formed of a portion of the sliding surface disposed at a position outward from the groove, and the hydraulic sealing portion being formed of a portion of the sliding surface disposed at a position inward from the groove.