A rotary seal comprising: a slinger attached to an inner diameter-side member; a core metal attached to an outer diameter-side member; and a seal body including a seal member joined to the core metal, wherein the slinger includes a slinger-cylindrical portion fitted to an outside of the inner diameter-side member and an outward flange portion extending radially outward from an end of the slinger-cylindrical portion in a direction parallel to an axial direction along a rotary shaft of the inner diameter-side member, the core metal includes a core-metal cylindrical portion fitted to an inside of the outer diameter-side member and an inward flange portion extending radially inward from an end of the core-metal cylindrical portion in a direction parallel to the axial direction, the seal member includes an axial lip brought into sliding contact with the outward flange portion of the slinger, a radial gap between an inner circumferential surface of the seal body and an outer circumferential surface of a joined member joined to the outward flange portion of the slinger includes a first gap portion and a second gap portion closer to the inward flange portion of the core metal than the first gap portion is, the outer circumferential surface that defines the first gap portion is a cylindrical or substantially cylindrical outer circumferential surface, the radial gap in the first gap portion is substantially constant in a direction parallel to the axial direction, the outer circumferential surface that defines the second gap portion is a conical or substantially conical outer circumferential surface, which is reduced in diameter as approaching the inward flange portion of the core metal in a direction parallel to the axial direction, and the radial gap in the second gap portion is gradually increased as approaching the inward flange portion of the core metal in a direction parallel to the axial direction, characterized in that an inclination angle IA defined by the conical or substantially conical outer circumferential surface with respect to the inner circumferential surface of the seal body is 5° ≤ IA ≤ 30°, when a length of the rotary seal in the direction parallel to the axial direction is L, a length L1 of the first gap portion in the direction parallel to the axial direction is L1 ≥ L × 0.2, a length L2 of the second gap portion in the direction parallel to the axial direction is L2 ≥ L × 0.2, and L1 + L2 ≤ L × 0.8, and a radial length H of the first gap portion is set to 0.3 mm ≤ H ≤ 1.0 mm. a slinger attached to an inner diameter-side member; a core metal attached to an outer diameter-side member; and a seal body including a seal member joined to the core metal, wherein the slinger includes a slinger-cylindrical portion fitted to an outside of the inner diameter-side member and an outward flange portion extending radially outward from an end of the slinger-cylindrical portion in a direction parallel to an axial direction along a rotary shaft of the inner diameter-side member, the core metal includes a core-metal cylindrical portion fitted to an inside of the outer diameter-side member and an inward flange portion extending radially inward from an end of the core-metal cylindrical portion in a direction parallel to the axial direction, the seal member includes an axial lip brought into sliding contact with the outward flange portion of the slinger, a radial gap between an inner circumferential surface of the seal body and an outer circumferential surface of a joined member joined to the outward flange portion of the slinger includes a first gap portion and a second gap portion closer to the inward flange portion of the core metal than the first gap portion is, the outer circumferential surface that defines the first gap portion is a cylindrical or substantially cylindrical outer circumferential surface, the radial gap in the first gap portion is substantially constant in a direction parallel to the axial direction, the outer circumferential surface that defines the second gap portion is a conical or substantially conical outer circumferential surface, which is reduced in diameter as approaching the inward flange portion of the core metal in a direction parallel to the axial direction, and the radial gap in the second gap portion is gradually increased as approaching the inward flange portion of the core metal in a direction parallel to the axial direction, characterized in that an inclination angle IA defined by the conical or substantially conical outer circumferential surface with respect to the inner circumferential surface of the seal body is 5° ≤ IA ≤ 30°, when a length of the rotary seal in the direction parallel to the axial direction is L, a length L1 of the first gap portion in the direction parallel to the axial direction is L1 ≥ L × 0.2, a length L2 of the second gap portion in the direction parallel to the axial direction is L2 ≥ L × 0.2, and L1 + L2 ≤ L × 0.8, and a length L1 of the first gap portion in the direction parallel to the axial direction is L1 ≥ L × 0.2, a length L2 of the second gap portion in the direction parallel to the axial direction is L2 ≥ L × 0.2, and L1 + L2 ≤ L × 0.8, and a radial length H of the first gap portion is set to 0.3 mm ≤ H ≤ 1.0 mm.