The purpose of the present invention is to provide a sealing device which has forward and reverse screw threads exhibiting a fluid-pumping action provided on a sliding portion of a seal lip, such that the pumping action is less susceptible to deterioration even with increasing wear on the screw threads and such that leakage of droplets from the screw threads is minimized. To achieve this, the forward and reverse screw threads which exhibit a pumping action on sealing fluid are arranged in a circle on the air-side lateral surface of the sliding portion of the seal lip. The forward and reverse screw threads each have a shape gradually increasing in thread height from the leading end of the lip to the air side. The forward screw threads and/or reverse screw threads are provided with seal protrusions for preventing leakage of droplets.