A sealing device includes a stationary side installation ring fixed to a stationary side member, a rotation side installation ring fixed to a rotation side member, a stationary side lip integrally provided on the stationary side installation ring and slidably contacting the rotation side installation ring, rotation side lips integrally formed on the rotation side installation ring and slidably contacting the stationary side installation ring, and a pulsar ring for a rotary encoder integrally formed on the rotation side installation ring, and magnetized to be multipolar. The rotation side installation ring includes first and second rotation side installation rings which are attached to each other. The rotation side lips are provided on the first rotation side installation ring at a relatively inner side. The pulsar ring is provided on the second rotation side installation ring at a relatively outer side.