A sealing device in which a magnetic encoder is protected so as to improve detecting precision and reliability, without increasing the number of parts and assembling time and without enlarging a setting space, the sealing device is structured such that a detected portion is arranged in the sealed fluid side of an annular member. A first annular member fitted to a shaft is formed with an axial direction portion and diametrical direction portions extending in the inward and outward diametrical directions from the axial direction portion. One of the diametrical direction portions supports the detected portion in the sealed fluid side. A seal lip is in slidable contact with the other diametrical direction portion for sealing, and the seal portion is formed with the seal lip and the micro space.