The invention provides a sealing device capable of suppressing leakage of a fluid to be sealed while reducing rotary torque regardless of rotational direction. In a sealing ring (100) slides against aside wall surface on a low-pressure side of an annular groove, a dynamic pressure generating groove (120) that includes a first groove (121) having a constant width in a radial direction and extending in a circumferential direction and a second groove (122) extending from a center position of the first groove (121) to an inner circumferential surface and guiding a fluid to be sealed into the first groove (121) is provided on a sliding surface side which slides against the side wall surface. The first groove (121) is provided at a position within a sliding region in which the sealing ring slides against the side wall surface.