A sealing device comprising: an annular reinforcement ring around an axis; an annular elastic portion around the axis, the annular elastic portion being attached to the reinforcement ring, being formed of an elastic material, and including a lip portion; and an annular protective ring around the axis, the annular protective ring being adapted to be fitted to an inner periphery side of the reinforcement ring, wherein the reinforcement ring includes a reinforcement ring tubular portion formed in a tubular shape around the axis, and the protective ring includes a protective ring tubular portion formed in a tubular shape around the axis, and an engagement portion provided on an outer peripheral surface of the protective ring tubular portion, the engagement portion being adapted to engage with the inner periphery side of the reinforcement ring, wherein the elastic portion includes a gasket portion attached to the reinforcement ring tubular portion, the engagement portion is adapted to engage with the gasket portion on an inner periphery side of the reinforcement ring tubular portion, the reinforcement ring includes a reinforcement ring disk portion extending from one end portion of the reinforcement ring tubular portion in a direction of the axis toward an inner periphery side, and the protective ring is adapted to be fitted to the inner periphery side of the reinforcement ring tubular portion from a side of another end portion of the reinforcement ring tubular portion in the direction of the axis, the sealing device being characterized in that the engagement portion is formed in a recessed groove shape on the outer peripheral surface of the protective ring tubular portion, the engagement portion includes an upstanding wall portion on the outer peripheral surface of the protective ring tubular portion, the upstanding wall portion facing the side of the another end portion of the reinforcement tubular portion when in the usage state of the sealing device, and the upstanding wall portion is configured to bite into an inner peripheral surface of the gasket portion when the sealing device is in its usage state. an annular reinforcement ring around an axis; an annular elastic portion around the axis, the annular elastic portion being attached to the reinforcement ring, being formed of an elastic material, and including a lip portion; and an annular protective ring around the axis, the annular protective ring being adapted to be fitted to an inner periphery side of the reinforcement ring, wherein the reinforcement ring includes a reinforcement ring tubular portion formed in a tubular shape around the axis, and the protective ring includes a protective ring tubular portion formed in a tubular shape around the axis, and an engagement portion provided on an outer peripheral surface of the protective ring tubular portion, the engagement portion being adapted to engage with the inner periphery side of the reinforcement ring, wherein the elastic portion includes a gasket portion attached to the reinforcement ring tubular portion, the engagement portion is adapted to engage with the gasket portion on an inner periphery side of the reinforcement ring tubular portion, the reinforcement ring includes a reinforcement ring disk portion extending from one end portion of the reinforcement ring tubular portion in a direction of the axis toward an inner periphery side, and the protective ring is adapted to be fitted to the inner periphery side of the reinforcement ring tubular portion from a side of another end portion of the reinforcement ring tubular portion in the direction of the axis, the sealing device being characterized in that the engagement portion is formed in a recessed groove shape on the outer peripheral surface of the protective ring tubular portion, the engagement portion includes an upstanding wall portion on the outer peripheral surface of the protective ring tubular portion, the upstanding wall portion facing the side of the another end portion of the reinforcement tubular portion when in the usage state of the sealing device, and the upstanding wall portion is configured to bite into an inner peripheral surface of the gasket portion when the sealing device is in its usage state.