A sealing device includes a mounted part to be mounted to the inner peripheral surface of the shaft hole, a cylindrical part disposed radially inside the mounted part, a seal lip portion extending from the cylindrical part and in contact with the outer peripheral surface of the rotational shaft, a bellows part connecting the mounted part and the cylindrical part, and an annular sliding member made of a resin and disposed radially inside the cylindrical part, the outer peripheral surface of the rotational shaft being slidable on the annular sliding member.